"We think they are heading toward weaponiz[ing] these missiles, which obviously we want to dissuade them from doing," the retired four-star Marine general told The Washington Times, explaining why U.S. officials dramatically shifted from years of focus on guarding against longer-range intercontinental ballistic missiles (ICBMs).

Gen. Jones also acknowledged that the policy shift announced on Thursday will pay "an ancillary benefit" to U.S. efforts to improve relations with Moscow, taking issue with a statement by White House press secretary Robert Gibbs that the change was "not about Russia."

"The fact is, there is clearly a relationship here in all of these issues," he said. "We are trying to reset the relationship with Russia, based on one of mutual respect and mutual interest."

In a wide-ranging interview Friday afternoon in his West Wing office, Gen. Jones said the government's top national security leaders met about 50 times since March before unanimously agreeing to scrap a 2006 Bush administration plan to put 10 long-range, ground-based interceptor missiles in Poland and a related radar tracking site in the Czech Republic. They are to be replaced by ship-based radar and interceptors better able to protect Europe from shorter-range missiles, he said.

The key driver, he said, was intelligence showing that Iran is stressing development of medium- and intermediate- range missiles that could reach the Middle East or Western Europe and is focusing less on ICBMs with ranges greater than 3,500 miles that might one day reach the United States.

"We concluded, the intelligence community concluded and recommended that the previous threat estimates about Iran's capabilities, vis-a-vis an ICBM, were not as imminent as we thought, which is to say the capability is further out," Gen. Jones said.

"The intermediate-range capability of Iranian technology is higher than we thought, which puts Europe at risk and many of our friends in the Gulf at risk," he said.

The new intelligence included a "pattern of Iranian testing and our observation of the tests, and the obvious range improvements they were getting, coupled with what we think is a plan to weaponize, maybe with nuclear warheads," he added.

Gen. Jones did not elaborate on the types of missiles, but said that "what we're talking about is the family of missile testing that allows us to conclude that it is the intermediate threat that is closer than we thought."

The Air Force's National Air and Space Intelligence Center stated in its annual report released in April that Iran has an "extensive missile development program" that includes the Shahab-3 and extended-range versions, as well as a new solid-fuel missile with a range of 1,240 miles enough to hit targets throughout Europe and the Middle East.

The report said Iran could have an ICBM by 2015.

However, two administration officials said the new intelligence is outlined in a May 2009 National Intelligence Estimate that concluded that Iran would not have a long-range missile before 2020.

U.S. estimates of missile threats have been of mixed reliability. In 1998, an intelligence assessment gauged that no nation outside the established nuclear powers would have a long-range missile by 2015. Shortly after the assessment, in August 1998, North Korea test-fired its first intercontinental-range Taepodong missiles.

While scrapping the Bush plan, the Obama administration wants to defend Europe by deploying Navy Aegis radar-equipped ships featuring Standard Missile-3 interceptors, which are less capable against long-range missiles but can stop medium-range missiles.

Less-capable radar will be deployed some place in the Caucasus region to replace the planned high-powered radar in the Czech Republic, which was troubled by a "public opinion problem," Gen. Jones said.

A subsequent phase would include deploying a land-based version of the SM-3, possibly in Poland, and more advanced SM-3s, including future versions that can hit long-range missiles, over the next 10 years.

The new plan means that defenses against Iranian missiles can be in place throughout Europe six or seven years sooner than under the abandoned European plan, Gen. Jones said.

"This package is a much more, I won't say nuanced, but phased approach that can be ramped up or ramped down any way we want, based on a new threat estimate," he said.

Efforts by Iran to develop longer-range missiles would be detected, he said. "There's not much the Iranians can do in terms of developing an ICBM that we won't know about," he said. "It just requires testing, and you can tell when they get into that envelope."

Gen. Jones also said the new policy "factored in some geopolitical issues with regard to developing an emerging relationship, hopefully a good one, with the Russians," as well as plans to "reinvigorate the strategic value of the North Atlantic Treaty Organization." Gaining Moscow's cooperation in dealing with the "imminent threat from Iran" is one of the priorities for the administration, he added.

He said the new policy was reached "independent of how we think about the Russians" and was based on the right national security policies for the United States. But "an ancillary benefit to the solution set which we think is the right solution, regardless of how the Russians feel about it, was that we could in fact do something that the Russians considered to be important. But it wasn't the driver by far."

The focus on near-term threats of Iranian missiles "could also take off the table some of the things the Russians were concerned about, but without affecting our ability to reinforce Article Five of NATO and provide for territorial defense," he said.

Critics of the Obama administration's decision to cancel the European sites say it will be viewed as a concession to Moscow that may not be reciprocated.

Also, the new system is designed to defend Europe and the Middle East, but will not be capable of stopping a long-range Iranian missile fired at the continental United States.

"It appears to me the administration has made a risk assumption and they are willing to bet the Iranians will not develop a long-range-missile capability in the near future," said retired Air Force Lt. Gen. Henry Obering, former director of the Pentagon's Missile Defense Agency.

"If the Iranians fly a 4,000-kilometer-range missile in the next six months, we're in trouble. We can't handle that," he said.

Gen. Obering said he views the new program as "rolling back" the earlier plan to deploy anti-ICBM interceptors in Poland.

"I see this as providing not as much defense, and it certainly can't defend the United States," he said.

The program also will include more technical risk because the more advanced versions of the SM-3 are "paper missiles" at this point and have not been tested.

Also, using less-capable radar, including sensors on unmanned aerial vehicles, will not be capable of identifying multiple warhead missiles, he said.

Eric Edelman, who was undersecretary of defense for policy in the Bush administration and who oversaw the 2006 missile-defense plan, said the new intelligence is questionable.

The National Air and Space Intelligence Center's missile report indicated that Iran could deploy a long-range missile by 2015 five years before advanced SM-3s would be in place to defend against it.

"President Obama reiterated that unless the assessment changed, we should move forward [with long-range interceptors]," Mr. Edelman said in an interview. "What has changed? It seems to me the administration needs to clarify (in an unclassified or classified setting) what has led to the different assessment."

The new plan also is expected to be widely viewed as "a preemptive concession to the Russians" that could have negative repercussions throughout NATO and especially in Central Europe, as well as among allies in the Gulf and Northeast Asia, including the untested new government in Japan, Mr. Edelman said.

"It would seem unwise to announce this move just as we are about to 'engage' the Iranians" in talks, he added.

As for the Russians, Mr. Edelman, now with the Center for Strategic and Budgetary Assessment, said official statements from Moscow indicate that there may not be matching concessions from Russia.

However, news reports from Moscow said Friday that the Russian military will not go through with threats to deploy advanced short-range Iskander missiles in the Russian enclave of Kaliningrad, as threatened by Russian leader Vladimir Putin in response to the planned U.S. missile-defense site in Europe.

Defense Secretary Robert M. Gates on Saturday lashed out at critics of the new missile-defense plan and insisted it was not a concession to Russia. "I believe this is a very pragmatic proposal. I have found since taking this post that when it comes to missile defense, some hold a view bordering on theology that regards any change of plans or any cancellation of a program as abandonment or even breaking faith," Mr. Gates, who served as defense secretary in the Bush administration, wrote in an opinion article for the New York Times, according to Reuters news agency.

Politically, the abandonment of the Europe site also set the stage for progress in reaching a new strategic arms agreement with Russia. Moscow vehemently opposed the European missile site as posing a threat to its strategic missile capability and had made canceling the program a precondition for arms talks.

The Bush administration then moved ahead with a limited missile-defense system of interceptors based at Fort Greeley, Alaska, and at Vandenberg Air Force Base, Calif., accompanied by two other new systems: a Navy ship-based system deployed on Aegis battle-management-equipped warships and built on the SM-3, and a newer Army system called the Theater High-Altitude Area Defense.

Both the Aegis and THAAD are designed to hit the warheads from short- and medium-range missiles, like Iran's Shahab-3.

Patriot anti-missile systems have been deployed by the United States and several allies for the past decade. The systems, however, were originally designed as anti-aircraft missile systems and were enhanced to provide limited capabilities against short-range missiles like the Scud.

The shift in missile-defense policy was signaled earlier this year when the Pentagon announced that it was cutting the number of planned long-range interceptors from 44 to 30 at the Alaska and California bases.