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

Russia is continuing to prepare for an invasion into Ukraine "in coming hours or days," a senior U.S. administration official told reporters on a call Monday. 

The big question now is whether Putin’s move to put security forces on the ground in the separatist region constitutes an invasion in the eyes of the west, therefore triggering the severe sanctions Western countries have been threatening.

The administration is still "observing and assessing" exactly what Russia is doing, the official said, adding that there will likely be more sanctions on Tuesday. 

When pressed by reporters on whether Putin started an invasion or triggered sanctions with his move on Monday, the official responded that Russian troops have been in the region for years.

The senior administration official heavily criticized the speech Putin made Monday as making "clear his true design," which was to persuade Russian citizens to "justify war."

"This wasn't a speech just about Russia's security," the official said. "It was an attack on the very idea of a sovereign and independent Ukraine. He made clear that he views Ukraine historically as part of Russia and made a number of false claims about Ukraine's intention that seems designed to excuse possible military action. This was a speech to the Russian people to justify a war. In fact, he once again explicitly threatened one."

-ABC News' Chief White House Correspondent Cecilia Vega and Justin Gomez

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