MOSCOW 

Finland and Sweden joining NATO would pose a threat to Russia's security, a Kremlin spokesman said on Thursday, as the two countries – troubled by the Ukraine war – signaled their clearest moves yet to seek membership.

Apart from creating threats to Russia, NATO's expansion eastward would “not contribute to security in Eurasia," Dmitry Peskov told reporters in Moscow.

Asked what Russia might do in response, Peskov said it would depend on the degree of advancement of the alliance's military infrastructure to Russia’s borders. Finland and Russia share a 1,300-kilometer (810-mile) border.

"We will analyze the situation with Finland's (possible) accession to NATO and will develop the necessary measures to ensure security," he said.

In a statement released Thursday, Finnish leaders say they plan to apply for NATO membership as soon as possible. Similar moves are widely expected by Sweden.

Russia has long warned against Finland and Sweden joining NATO, and the public and leaders in both countries were largely opposed until Feb. 24, when Russia started its war on Ukraine. Then the tide turned.

In launching its war on Ukraine, Moscow repeatedly warned of the “threat” of it joining NATO, though its membership process was only just beginning.