Russia has retaliated against new U.S. sanctions by ordering 755 American diplomats to leave - a move that will create a fresh crisis in the relationship between the two countries.

Days after both houses of the U.S. Congress voted almost unanimously to impose fresh sanctions on Moscow, Vladimir Putin said he was responding to “unlawful” behavior by Washington, the Independent reported.

“The American side has made a move which, it is important to note, hasn’t been provoked by anything, to worsen Russian-U.S. relations. [It includes] unlawful restrictions, attempts to influence other states of the world, including our allies, who are interested in developing and keeping relations with Russia,” Putin told the Rossiya 1 TV channel.

“We’ve been waiting for quite a long time that maybe something would change for the better, we had hopes that the situation would change. But it looks like, it’s not going to change in the near future... I decided that it is time for us to show that we will not leave anything unanswered.”

The U.S. sanctions bill also included measures against Iran and North Korea and was passed over Russia’s 2014 annexation of Crimea and its alleged interference in the 2016 U.S. election.

An official at the U.S. Embassy in Moscow said there were about 1,100 diplomatic and support staff in Russia, including U.S. citizens and Russians, Reuters reported last week.

A U.S. State Department official called Russia's decision to expel the diplomats "a regrettable and uncalled-for act".

Earlier on Sunday, Deputy Foreign Minister Sergei Ryabkov said the vote for the sanctions was the “last drop” and said Moscow would retaliate “in kind".

“We have a very rich toolbox at our disposal. It would be ridiculous on my part to start speculating on what may or may not happen,” Rybakov told ABC. “I can assure you that different options are on the table and consideration is being given to all sorts of things.”