U.S. President Joe Biden agreed to deepen security ties with his Finnish counterpart Sauli Niinisto on Friday, but stopped short of making any formal guarantees to the country nervously watching Russia's invasion of Ukraine.

Both men also stopped short of saying Finland would seek to join NATO or become a major non-NATO ally of the United States, a designation granting enhanced security cooperation.

Yet during an hour-and-a-half long White House meeting, Biden called Finland a "strong defense partner" helping a "united trans-Atlantic response to holding Russia accountable."

Russia does not want Finland or Sweden to join NATO and just a week ago Moscow made its latest warning to them of "serious military-political consequences" if they did. Niinisto has maintained that Finland, a European Union member, has a right to seek NATO membership but tamped down talk of doing so in the midst of a crisis.

Ukraine's government had said it wanted to seek membership in the U.S.-led military alliance and Moscow had wanted the West to guarantee Kyiv would never become a member.

"Finland has stirred clearly towards closer cooperation with the United States," Niinisto told reporters after thanking Biden for "leadership" in "very difficult times."

He said the United States and Nordic countries would "initiate a clear process to step up defense and security cooperation" after a meeting with Biden that included a call to Magdalena Andersson, the prime minister of Finland's western neighbor Sweden. Andersson and Niinisto plan to meet in Finland on Saturday.

The war in Ukraine has roused concerns among other European countries neighboring Russia. Finland shares a 833-mile (1,340-km) border with Russia and opinion polling shows support for full membership of NATO has grown since Russian President Vladimir Putin ordered his forces into Ukraine on Feb. 24.

"This process of security cooperation is about concrete security and defense factors, not so much about memberships," Niinisto said after meeting Biden. But he added that Finland meets the criteria to join NATO.

"The Presidents committed to start a process that would strengthen U.S.-Finnish security cooperation, which would be conducted in close consultation with other Nordic countries," the White House said in a statement that alluded to NATO's policy of welcoming new members who meet its requirements. "The Presidents also discussed the importance of NATO's Open Door policy."

Deeper security ties will be on display when Finnish defense minister Antti Kaikkonen travels to the United States next week, where he will meet with his U.S. counterpart Lloyd Austin and visit Lockheed Martin facilities in Texas.

Last month, Finland sealed a $9.4 billion deal to buy dozens of F-35 stealth warplanes from the United States. Kaikkonen also plans to visit a U.S. air base in Florida to see the planes.

Finland, which was part of the Swedish kingdom until 1809 and then was under Russia's control until gaining independence in 1917, has historically sought to preserve cordial relations with Moscow.

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

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