Standing next to Polish President Bronislaw Komorowski, Obama said the U.S. would rotate more American troops into the region and called on Congress to provide up to $1 billion to support the effort.

“Under this effort, and with the support of Congress, the United States will preposition more equipment in Europe,” Obama said at in Warsaw’s Belweder Palace.

Obama’s announcement came at the start of a three-country swing through Europe. The White House said the funding would be used to increase military exercises and training missions, as well as rotations of air and ground forces, on the continent.

Officials said Obama was also seeking to ramp up U.S. Navy participation in NATO deployments in the Black and Baltic Seas, plus working to boost the military capacity of non-NATO countries that sit on Russia’s border, including Ukraine, Georgia and Moldova.

Speaking the day before Obama was scheduled to meet for the first time with Ukraine’s newly elected president, Petro Poroshenko, Obama said he wants both the U.S. and Ukraine to have good relations in the future with Russia.

He called on Moscow to avoid further provocation in Ukraine, warning that such provocations would be met with further consequences. The U.S. and Europe have already levied sanctions against Russian officials, but are holding off on further sanctions amid signs Russia may be willing to accept the legitimacy of Ukraine’s new government.

“Russia has a responsibility to engage constructively with the government in Kiev,” Obama said.

NATO secretary general Anders Fogh Rasmussen hailed Obama’s announcement that the U.S. would bolster its presence on the continent.

“The United States has reacted swiftly after Russia’s illegal military actions in Ukraine,” Rasmussen said as he met with NATO defense ministers in Brussels. “And I appreciate that other allies have followed so that we can announce that all 28 allies are now contributing to reassurance measures.”

Obama’s visit to Warsaw coincides with the 25th anniversary of Poland emerging from communism. Obama also planned to meet with Group of 7 leaders in Brussels before heading to France to mark the 70th anniversary of the D-Day invasion that eventually led to Allied victory in World War II.

Later Tuesday, Obama and Komorowski planned to hold discussions on central European security with leaders from Bulgaria, the Czech Republic, Estonia, Croatia, Hungary, Latvia, Lithuania, Romania and Slovenia.

U.S. Secretary of State John Kerry was joining Obama for many of his events in Warsaw. During a separate meeting Tuesday with Poland’s foreign minister, Kerry said the crisis in Ukraine presents “a new moment of challenge for all of us.”

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“Events in Ukraine have unfortunately unleashed forces that we had all hoped had been put away, were behind us, and so it requires new vigilance and it requires clear commitment,” Kerry said.

Ukrainian President-elect Petro Poroshenko also planned to be in Warsaw this week and was scheduled to hold his first bilateral meeting with Obama. Those talks come a few days before Obama’s likely encounter with Russian President Vladimir Putin, who also planned to attend the events in Normandy.

White House officials said the anniversaries of both Poland’s post-communism elections and the WWII invasion had particular resonance given the ongoing tensions between Russia and Ukraine.

“We have to take the energy that we draw from those anniversaries and the inspiration we draw from those anniversaries, and use that to mobilize collective action going forward,” said Ben Rhodes, Obama’s deputy national security adviser.

Obama’s meeting with Poroshenko was scheduled for Wednesday. Poroshenko also planned to attend the D-Day events Friday with Putin and more than a dozen other heads of state. All eyes will be on body language and any interactions between them, with Europe and the U.S. condemning Russia’s actions in Ukraine and levying sanctions against Russian officials.

French President Francois Hollande invited all the leaders and was going to great pains to keep some distance between Obama and Putin on the eve of the Normandy visit. He was hosting a dinner with Obama in Paris on Thursday night, then another with Putin a couple of hours later.

“There will not be a trilateral dinner that evening between the three of them,” Rhodes said. “It’s just a one-on-one.”