US Secretary of State Antony Blinken warned Wednesday that Russian President Vladimir Putin could be preparing to send more forces toward Ukraine after massing tens of thousands of troops.

“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,” Blinken said on a visit to Kiev.

Blinken called on Putin to choose a “peaceful path” as the top US diplomat paid a solidarity visit to Ukraine amid invasion fears.

“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,” Blinken said.

The Biden administration said Wednesday it is providing an additional $200 million in defensive military aid to the country amid soaring fears of a Russian invasion.

A senior US State Department official said the assistance was approved in late December as part of American efforts to help Ukraine protect itself. Until Wednesday, however, the administration had refused to comment on it.

The official was not authorized to discuss the matter publicly before Blinken’s meetings in Kiev and spoke on condition of anonymity.

“We are committed to Ukraine’s sovereignty and territorial integrity and will continue to provide Ukraine the support it needs,” the official said. The official did not detail the contents of the aid package.

After talks last week failed to ease fears, the White House warned Tuesday that Russia was ready to attack Ukraine at “any point.”

It was a marked intensification of its threat assessment ahead of a meeting between Blinken and Russian Foreign Minister Sergei Lavrov expected in Geneva on Friday.

Hoping to show robust support ahead of the talks, the top US diplomat is making a one-day visit to Kiev Wednesday in a show of support for Ukraine.

He was greeted by Ukrainian officials on an icy moonlit tarmac and will later meet President Volodymyr Zelensky.

Blinken heads Thursday to Berlin for four-way talks with Britain, France and Germany to seek Western unity.

“We’re now at a stage where Russia could at any point launch an attack on Ukraine,” the White House’s Press Secretary Jen Psaki told reporters on Tuesday.

“No option is off the table,” she said, warning of an “extremely dangerous situation.”

And she said that Russian President Vladimir Putin “has created this crisis.”

Moscow has repeatedly denied that an invasion is planned.

In a call between the US and Russian top diplomats ahead of Blinken’s trip, the Russian foreign ministry said Lavrov had called on Blinken “not to replicate speculation about the allegedly impending ‘Russian aggression’.”

US State Department spokesman Ned Price said that Blinken “stressed the importance of continuing a diplomatic path to de-escalate tensions.”

And a US official, who spoke on condition of anonymity, said Blinken’s goal was to see “if there is a diplomatic off-ramp” and “common ground” where Russia can be persuaded to pull back from Ukraine.

With tens of thousands of Russian troops massing on Ukraine’s borders, efforts have intensified to prevent tensions escalating into a new European war.

However, in a joint press conference with visiting German Foreign Minister Annalena Baerbock on Tuesday, Lavrov said there would be no further negotiations until the West responds to its demands for sweeping security guarantees.

They include a permanent ban on Ukraine joining NATO.

Washington has rejected the demands.

While the United States and its European allies have no plans to meet a Russian attack against Ukraine with military force, the economic counter-measures would be unlike any used in the past, Washington says.

The US official said it was possible that Russia is not interested in a diplomatic solution.