Amid warnings of an impending Russian invasion of Ukraine, the US Air Force has deployed eight F-16 fighter jets to Romania.

The planes arrived at Borcea Air Base, 150 kilometers east of Bucharest, the Romanian Defense Ministry said.

They would join 150 US soldiers in joint exercises with the Romanian military, the statement said.

The maneuvers would last two weeks.

A few days ago, four US Navy F/A-18 Super Hornet fighter jets and 50 US soldiers arrived in Borcea.

They should also take part in the exercise.

Romania borders directly on Ukraine.

The US Air Force Command for Europe and Africa confirmed the deployment of the fighter jets to Romania.

The dispatched F-16 machines, the number of which was not mentioned in the announcement, are stationed at the US air force base in Spangdahlem in the Eifel.

The move serves "to strengthen NATO's collective defense capabilities and support NATO airspace surveillance," the statement said.

"The additional aircraft and crew will work closely with allies in the Black Sea region to bolster regional security amid current tensions caused by Russian troop deployments near Ukraine."

Washington believes invasion is possible "at any time."

In Romania, around 1,000 US soldiers and Stryker wheeled armored vehicles are also to reinforce the Romanian security forces.

In Bulgaria, the second Eastern European NATO country on the Black Sea, four Eurofighters from NATO country Spain are to help with airspace surveillance.

Naval maneuvers in the Black Sea near the Ukrainian coast are currently part of the Russian military threats surrounding Ukraine.

The US government considers a Russian invasion of Ukraine possible in the coming week and is therefore relocating around 3,000 more soldiers to the NATO partner country Poland.

"We are in a window where an invasion could begin at any time should Vladimir Putin decide to order it," National Security Advisor Jake Sullivan said at the White House on Friday.

"I will not comment on the details of our intelligence information.

But I want to be clear that it (the invasion) could start during the Olympics, although there is a lot of speculation that it would not happen until after the Olympics.”

Russia's embassy in the United States dismissed American warnings of an attack on Ukraine as unfounded.

"Alarmism" is being spread in the United States without any evidence to back up the claims, Russian Ambassador to Washington Anatoly Antonov said on Saturday.

The statements in Washington only showed that the US had stepped up its "propaganda campaign against our country," Antonov said.