Blinken visits Ukraine, Russia sends more troops

"I strongly, strongly hope that we can keep this on a diplomatic and peaceful path but, ultimately, that's going to be President Putin's decision."

On a visit to Kyiv on Wednesday, U.S. Secretary of State Antony Blinken said Russia could launch a new attack on Ukraine on "very short notice" but that Washington would pursue diplomacy as long as it could.

"As you all know very, very well, we have been engaged in the past couple of months in an intense focus on Ukraine because of the significant build up we've seen of Russian forces near the Ukrainian border, no provocation, no reason, except that we have a very significant force, we know that there are plans in place to increase that force even more on very short notice, and that gives president Putin the capacity also on very short notice to take further aggressive action against Ukraine."

Later, at a joint press conference with Ukraine's foreign minister, Blinken said Washington would keep providing defense assistance to Ukraine and renewed a promise of severe economic sanctions against Russia in the event of a new invasion.

"We will continue relentless diplomatic efforts to prevent renewed aggression and to promote dialogue and peace. At the same time, we continue to bolster Ukraine's ability to defend itself and make clear the costs that the United States and Europe will impose on Moscow if it rejects the diplomatic path that we've laid out and proceeds with an unwarranted, unprovoked, unacceptable invasion or destabilization of Ukraine."

Adding to the tension, Russia moved additional troops into Belarus this week for what it calls joint military exercises, giving it the option of attacking Ukraine from the north, east and south.

Moscow continues to deny any intention to invade Ukraine and said the U.S. arms deliveries to Ukraine was increasing the tension, and that it was still waiting for a written response to its sweeping demands for security guarantees from the West.

Blinken was scheduled to meet with Russian Foreign Minister Sergei Lavrov on Friday, which one Russian foreign policy analyst called "probably the last stop before the train wreck."