U.S. President Joe Biden and his Finnish counterpart Sauli Niinisto agreed on Friday to deepen ties but stopped short of making public security guarantees or suggesting that Finland could join NATO after Russia's Ukraine invasion.

Biden said during the White House meeting that Finland is a "strong defense partner" involved in a "united trans-Atlantic response to holding Russia accountable" for what he called an attack on global peace.

"We are really living in very difficult times," said Niinisto. "I want to thank you also for the leadership you have showed. We need it now."

Talks between the two leaders came as that war has roused fresh concern for other European countries bordering Russia.

Finland already cooperates with NATO, but is not a member, though support for full membership has grown in the country since Russian President Vladimir Putin's invasion of Ukraine.

The United States could also declare Finland a major non-NATO ally and step up weapons sales to the country, which shares an 833-mile (1,340-km) border with Russia.

Last month, Finland sealed a $9.4 billion deal to buy dozens of F-35 stealth warplanes from the United States, in a sign of the Finnish military's growing ties to NATO.

But Finland, a European Union member which was part of the Swedish kingdom until 1809 and then was under Russia's control until gaining independence in 1917, has also sought to preserve friendly relations with Moscow.

Russia does not want Finland to join NATO, but Niinisto has said the country retains the right to apply for membership. Still, he has tamped down talk of such a step happening in the midst of a crisis.

Ukraine's government said it wanted to seek NATO membership prior to Putin's invasion.

Defense topics were expected to be a major topic in the Oval Office talks.

The Finnish public is growing fonder of the idea of joining NATO. A poll by public broadcaster Yle last Monday said 53% of Finns support joining, compared with 28% when the Helsingin Sanomat newspaper asked the question in late January.

Finland's government has sought to calm campaigns to join the U.S.-led defense bloc. Niinisto said in a statement that people should "keep a cool head and assess carefully the impact of the changes that have already taken place and of those that might still happen."

During a small portion of the Oval Office meeting open to reporters, Biden said his predecessor Barack Obama often said the world would be fine if they left matters up to Nordic countries.

"Well, we usually don't start wars," Niinisto replied.