Russia-Ukraine updates: US to ban Russian carriers from its airspace

The U.K. will announce new sanctions against Russia on Tuesday "in response to their breach of international law and attack on Ukraine's sovereignty and territorial integrity," U.K. Foreign Secretary Liz Truss said Monday. 

Earlier in the day, Truss said the recognition of the Donetsk People's Republic and the Luhansk People's Republic as independent states "demonstrates Russia's decision to choose a path of confrontation over dialogue."

"We will not allow Russia's violation of its international commitments to go unpunished," Truss said.

The decision to recognize Donetsk and Luhansk in eastern Ukraine was an "ill omen" and a flagrant breach of international law, U.K. Prime Minister Boris Johnson said.

Johnson spoke to Ukrainian President Volodymyr Zelenskyy on Monday evening. Johnson outlined "his grave concern at recent developments in the region" and told Zelenskyy "that he believed an invasion was a real possibility in the coming hours and days," according to a Downing Street spokesperson. 

"The leaders agreed that the West needed to support Ukraine in the event of an invasion but should continue to pursue a diplomatic solution until the last possible second," the spokesperson said.

-ABC News’ Guy Davies and Somayeh Malekian

Russia has published the mutual defense treaty it has concluded with the separatist regions.

The “friendship, cooperation and mutual aid” treaty states that the two will come to each other’s defense in the case of attack and authorizes Russia to build military infrastructure on the separatist territory -- inside an internationally recognized part of Ukraine.

The treaty also says that Russia and the separatist forces will guards its borders jointly, meaning Russian forces will openly deploy along the frontline.

It lays the ground for a substantial open Russian military deployment into the separatist territory, where a lot of covert Russian troops were already located.

-ABC News’ Patrick Reevell

The U.S. administration has urged Ukrainian President Volodymyr Zelenskyy to head to Lviv, in the western part of the country, for his safety, a U.S. official told ABC News.

-ABC News’ Chief Global Affairs Correspondent Martha Raddatz

President Joe Biden spoke with French President Emmanuel Macron and German Chancellor Olaf Scholz on Monday afternoon, in which all three leaders "strongly condemned" Russian President Vladimir Putin’s decision to recognize separatist regions in Ukraine as independent, the White House announced in a statement. 

"The leaders strongly condemned President Putin’s decision to recognize the so-called DNR and LNR regions of Ukraine as 'independent,'" the statement read. "They discussed how they will continue to coordinate their response on next steps."

NATO Secretary General Jens Stoltenberg also condemned Putin’s decision, stating, "This further undermines Ukraine’s sovereignty and territorial integrity, erodes efforts towards a resolution of the conflict, and violates the Minsk Agreements, to which Russia is a party."

-ABC News' Patrick Reevell and Christine Theodorou