US President Barack Obama, left, looks on as Polish President Bronislaw Komorowski gestures during a meeting with Polish and US soldiers at the military airport in Warsaw, Poland, on Tuesday, June 3, 2014. (AP Photo/Alik Keplicz)

WARSAW, Poland: President Barack Obama announced Tuesday that the United States plans to boost its military presence in Europe as tensions simmer in the region over Russia’s actions in Ukraine.

Standing next to Polish President Bronislaw Komorowski, Obama said the US 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 Warsaw’s Belweder Palace.

If approved, the funding will be used to increase military exercises and training missions on the continent, as well as rotations of air and ground forces, the White House said. Officials said Obama was also seeking to ramp up US 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.

Obama’s announcement came at the start of a three-country swing through Europe stepped in both historical significance and regional anxiety over the crisis in Ukraine.

A day before his first face-to-face encounter with Ukraine’s newly elected president, Petro Poroshenko, Obama said he wants both the US and Ukraine to have good relations with Russia. But in a warning to Moscow, Obama said the US has contingency plans to protect every member of NATO, and has been steadily developing those plans in recent years.

“Our contingency plans are not just pieces of paper on a shelf,” Obama said, adding that the US must and does have the ability to put those plans into effect if needed.

At the same time, he called on other NATO members to step up by increasing their own role in the alliance’s collective defense, even as he acknowledged that the US has greater capabilities to bear that burden than its smaller allies.

“Everyone has the capacity to do their fair share, to do a proportional amount to make sure we have the resources, the planning, the integration, the training in order to be effective,” Obama said.

To that end, Komorowski announced that Poland intends to increase its own defense budget, up to 2 percent of the nation’s gross domestic product. “It means it’s a very tangible, very clear engagement,” Komorowski said through a translator.

The cautionary notes from Obama and Komorowski came just a few days before a potential encounter between Obama and Russian President Vladimir Putin, who also planned to be in France for the 70th anniversary of the D-Day invasion that eventually led to Allied victory in World War II. Obama and Putin haven’t met in person since the crisis began and have no meetings together scheduled, but White House officials haven’t ruled out that they could cross paths.

Calling his relationship with Putin “businesslike,” Obama said he would emphasize if he were to run into Putin during the event that Russia should work to de-escalate the situation with Ukraine, but that the US stands ready to impose further costs if Putin chooses a difference course.

“We are interested in good relations with Russia. We are not interested in threatening Russia,” Obama said.

The US and Europe have already levied sanctions against Russian officials, but are holding off on further sanctions amid Putin’s vow to respect the results of Ukraine’s recent presidential election.

NATO secretary general Anders Fogh Rasmussen hailed Obama’s announcement of a bolstered US 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 D-Day anniversary.

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.

US 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.”

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.