Russia-Ukraine updates: 2 US veterans who joined Ukrainian forces missing

The U.S. will "keep moving heaven and earth" to supply aid to Ukraine, Secretary of Defense Lloyd Austin said on Tuesday at a meeting of the Ukraine Security Consultative Group, which includes military representatives from about 40 countries.

“Ukraine clearly believes it can win. And so does everyone here,” Austin said in his opening remarks at Ramstein Air Base in Germany. “I know that we’re all determined to do everything we can to support Ukraine’s needs as the fight evolves.”

Austin said the group would seek to leave with a common understanding of “Ukraine’s near term security requirements, because we’re going to keep moving heaven and earth so that we can meet them.”

Russian forces appeared to be moving to encircle “heavily fortified” Ukrainian positions in the east, the U.K. Ministry of Defense said on Tuesday.

“The city of Kreminna has reportedly fallen and heavy fighting is reported south of Izium, as Russian forces attempt to advance towards the cities of Sloviansk and Kramatorsk from the north and east,” the ministry said in its latest intelligence update.

Ukrainian forces in Zaporizhzhia were preparing for an attack from the south, the ministry said.

Ukrainian President Volodymyr Zelenskyy warned European superpowers that the fate of the continent is being determined by the conflict currently unfolding in Ukraine.

The future of global security and democracy in Europe are currently being decided in Ukraine, Zelenskyy said during his nightly address on Monday.

"The lessons of history are well known," he said. "If you are going to build a millennial Reich, you lose. If you are going to destroy the neighbors, you lose. If you want to restore the old empire, you lose. And if you go against the Ukrainians, you lose."

Ukraine Minister of Foreign Affairs Dmytro Kuleba tweeted Monday that Russia is attempting to make it seem like the world is on the brink of World War III because it has lost its "last hope to scare the world off supporting Ukraine."

"Thus the talks of 'real danger' of WWIII," Kuleba wrote "This only means Moscow senses a defeat in Ukraine."

-ABC News' Max Uzol and Christine Theodorou

In an interview with Russia's Channel One, Russian Foreign Minister Sergey Lavrov said NATO weapons supplied to Ukraine are essentially a proxy war and that Russian troops will consider the Ukrainian warehouses storing the weapons as legitimate targets.

"Of course, these weapons will be a legitimate target for the Russian armed forces, which operate as part of a special armed operation. And warehouses, including in western Ukraine, have become such targets more than once," Lavrov said Monday. "If NATO, in fact, goes to war with Russia, through a proxy, and arms this proxy, then in war as in war."

Lavrov also claimed that "the real position of Ukraine is determined in Washington, London and other Western capitals."

"Therefore, our political analysts say, why talk with [Ukrainian President Volodymyr Zelenskyy]'s team, we need to talk with the Americans, negotiate with them, reach some kind of agreement," Lavrov said.

-ABC News' Natalia Shumskaia