ALLINN, Estonia (AP) -- President Barack Obama is standing shoulder to shoulder with Baltic leaders in a show of solidarity with NATO allies who fear they could be the next target of Russia's aggression.

President Barack Obama, left, and Estonia's President Toomas Hendrik Ilves , right, smile as they attend a welcome ceremony at the Kadriorg Palace in Tallinn, Estonia (AP Photo/Mindaugas Kulbis)

As Obama opened a bilateral meeting Wednesday with Estonian President Toomas Hendrik Ilves, word emerged of a cease-fire agreement between Russian President Vladimir Putin and Ukrainian President Petro Poroshenko. But there were few details and no immediate reaction from the pro-Russian separatists in eastern Ukraine, adding further uncertainty to the regional crisis that brought Obama to the region.

After arriving in the early morning in Estonia's port capital of Tallinn, Obama was greeted by Ilves on a crisp and sunny morning at Kadriorg Palace, where Obama placed his hand over his heart as the U.S. national anthem played. The two leaders then inspected Estonian troops and shook hands with groups of flag-waving schoolchildren.

Inside the palace, Ilves said Obama's visit was crucial "especially in the current context."

The U.S. and Estonia are two of the four NATO countries that fulfill their pledges to contribute 2 percent of their gross domestic product to defense spending. Ilves said Obama's visit would help Estonians understand the importance of being part of the alliance, "especially all these years fighting for 2 percent and doing it, and people mumbling and grumbling, `Why do you have to do all that, look at them, they're not doing anything.'"

Obama becomes the second sitting American president to visit Estonia, following President George W. Bush, who traveled here in 2006. Obama wrote in a palace guest book that it was an honor to visit "a nation that shows what free people can achieve together."

"May we strengthen our friendship for future generations," Obama wrote.

Obama and Ilves were to take questions from reporters later Wednesday before holding broader security talks that include the leaders of Latvia and Lithuania.

Obama's daylong trip to Estonia comes ahead of a NATO summit this week at which allies will commit to a more robust response to Russia's incursion in Ukraine. Moscow's moves have sparked fears among member states on NATO's eastern flank that they could be Russian President Vladimir Putin's next target.

White House officials say Obama will reassure the Baltics that the U.S. would come to their defense it they were attacked. Under the NATO charter, an attack on one member is considered an attack on the entire alliance.

During the NATO summit in Wales starting Thursday, the alliance will also agree on a more robust rapid response force that will involve positioning more troops and equipment in the Baltics and elsewhere in Eastern Europe. It's unclear whether the plan will satisfy the concerns of the Baltic nations, who have been pressing NATO for permanent bases in the region.

Even before the Ukraine crisis, relations between the Baltic countries and Russia were chilly. Moscow routinely accuses them of discriminating against their Russian-speaking minorities.

About a third of Estonia's 1.3 million residents have Russian as their mother tongue. Many of them feel detached from Estonian society and get their news from Kremlin-controlled Russian TV stations.

The Baltics were invaded by the Soviet Union and Nazi Germany during World War II. After the Soviet Union crumbled, the Baltic countries turned to the West and joined the European Union and NATO in 2004, much to the chagrin of Russia.

Obama will depart Tallinn late Wednesday for Wales, which is hosting the two-day NATO summit.

(© 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed)