Putin abruptly summoned his top security officials as US warns war with Ukraine is imminent

• Putin convened an unscheduled meeting of Russia's security council on Monday.
• The US warned that Russia could invade Ukraine at any moment.

Russian President Vladimir Putin convened an unscheduled meeting with his country's top security officials on Monday as the US continues to warn that a war with Ukraine is imminent.

"This is a big security council," Kremlin spokesman Dmitry Peskov said, the state-run RIA news agency reported. Peskov also told reporters the meeting "is not a regular one" and that Putin will deliver a speech afterward.

Tensions between Russia, the West, and Ukraine have mounted in recent weeks, with US national security advisor Jake Sullivan warning on Monday morning that a Russian invasion of Ukraine was underway.

"All signs look like President Putin and the Russians are proceeding with a plan to execute a major military invasion of Ukraine," Sullivan told "Good Morning America." President Joe Biden on Friday also warned that he was "convinced" that a Russian invasion of Ukraine was likely.

Russia has long insisted that it has no plans to invade Ukraine, and that it only amassed hundreds of thousands of troops at Ukraine's border for training drills and as a precaution against what Putin called mounting US and NATO aggression.

Efforts to find a diplomatic solution to the Ukraine crisis have so far fallen short. French President Emmanuel Macron said on Sunday that Biden and Putin had tentatively agreed to a summit "on security and strategic stability in Europe," and the White House said Biden agreed to it as long as Russia doesn't invade Ukraine in the mean time.

However, the Kremlin denied Monday that Putin had committed to the meeting, saying there were "no concrete plans" for the US and Russian leaders to meet.

Biden convened a meeting of the US National Security Council on Sunday. The US has warned Putin that he will face consequences should Russia invade.