"Unfortunately there's a difference between what Russia says, and what it does, and what we're seeing is no meaningful pullback," he said on ABC News.

"On the contrary, we continue to see forces, especially forces that would be in the vanguard of any renewed aggression against Ukraine, continuing to be at the border, to mass at the border."

Blinken called the threat of an invasion "real" and reiterated Washington's call for Russia to de-escalate the situation.

"President Putin has put in place the capacity to act on very short notice," the top US diplomat said.

"He can pull the trigger -- he could pull it today. He could pull it tomorrow. He could pull it next week. The forces are there if he wants to renew aggression against Ukraine."

Blinken urged diplomacy to resolve the situation, but added: "We're prepared for diplomacy. We're prepared for aggression. We're prepared either way."

Later Wednesday the State Department announced that Blinken would travel to Munich this week for the annual Munich Security Conference on February 18-20.

During the conference, the department said, Blinken "will have the opportunity to discuss with allies and partners our coordinated, ongoing efforts to urge Russia to de-escalate and choose the path of diplomacy, as well as our readiness to impose severe costs should Russia further invade Ukraine."

Blinken's Russian counterpart, Foreign Minister Sergei Lavrov, is not expected to attend the conference.