But other deputies and analysts voiced skepticism Thursday about the effectiveness of the movement, called Go Russia, which was announced by Gennady Gudkov, a member of the pro-Kremlin A Just Russia party.

Gudkov said in interviews published late Wednesday that Go Russia, named after Medvedev's seminal article published a year ago, would be open to members of any political party but would be opposition-minded all the same.

"We will unite those who want to speed up reform. Our leaders won't do this themselves," he told Gazeta.ru.

He said the movement's founding session would be held Sept. 25.

Ilya Ponomaryov, another Just Russia deputy, said Medvedev's modernization plans needed more support in society.

"This movement can help a lot because Medvedev's supporters are everywhere," he told The Moscow Times.

A Kremlin spokeswoman said she would not comment on the plan. "This is the personal initiative of Gennady Gudkov," said the spokeswoman, who asked not to be identified, citing Kremlin policy.

Political analysts speculated that the move was an attempt by A Just Russia to widen its electoral base before next month's regional elections.

The party, formed under the Kremlin's auspices in 2006, has been criticized as a project aimed at taking votes from the Communists.

Now, analysts said, A Just Russia is eyeing both liberal and conservative voters at a time when Luzhkov, a founding member of United Russia, is the target of an unprecedented smear campaign on national television amid clear signals from the Kremlin that he should step down.

"These people are using the current crisis to woo voters away from United Russia," said Mikhail Vinogradov, head of the St. Petersburg Politics Fund, a think tank.

The conflict has raised fresh questions about Medvedev's relationship with Prime Minister Vladimir Putin, who chairs United Russia.

Analysts have said for some time that Medvedev, who belongs to no party, must form his own political base to stand in the 2012 presidential election.

But Vinogradov, who also works as an adviser to United Russia, said he doubted that Go Russia could unite enough people to eventually form a political party. "There will be too many contradictions," he said.

Communist Duma Deputy Viktor Ilyukhin said he would not participate in any movement supporting Medvedev.

"I am for modernization and technological innovation — but only without Medvedev," he said by telephone.

Ilyukhin complained that Medvedev had achieved little after being appointed Kremlin chief of staff in 2003 and first deputy prime minister in 2005.

"He has shown that he can say the right things but that he is unable to get results," Ilyukhin said.

Igor Yurgens, head of the Institute of Contemporary Development, a think tank chaired by Medvedev, said it was too late to form a pro-Medvedev party.

Speaking to reporters Wednesday, Yurgens said he had called for such a modernization party 18 months ago.

He said Putin could have stayed with United Russia and the country would have had a two-party system like in the United States.

"But it is already too late to form a party under Medvedev," he said, Interfax reported. The bureaucracy will not tolerate it."

But Georgy Bovt, a co-leader of Right Cause, a liberal opposition party, said forming the movement now was "better late than never."

Bovt, who said he would attend next week's founding congress, expressed skepticism that the movement would be a pro-Medvedev party, saying the president did not need that.

"If he decides to run [for president in 2012], he will do it with the support of Putin and United Russia. And if he doesn't run, he doesn't need a party either," he said.

Meanwhile, four leaders of the country's fractured liberal opposition vowed to unite to present a single candidate for the 2012 election.

Boris Nemtsov, Vladimir Ryzhkov, Vladimir Milov and Mikhail Kasyanov told reporters Thursday that they had signed an agreement to form a coalition called For a Russia Without Arbitrariness and Corruption.

They did not say who would be their candidate.

Kasyanov, who was prime minister under President Putin from 2000 to 2004, said the coalition planned to register as a party and attempt to take part in next year's Duma elections.

He acknowledged, however, that the chances of being placed on the ballot were slight. "We are not naive, and we understand that our political party won't be registered," he said, Interfax reported. "But our rights to do this are laid down in the Constitution, and we will fight for them."