President Donald Trump is preparing to expel dozens of Russian diplomats from the U.S. in response to the nerve-agent poisoning of a former Russian spy in the U.K., two people familiar with the matter said Saturday.

Trump agreed with the recommendation of advisers and the expulsions are likely to be announced on Monday, the people said, though they cautioned that Trump's decision may not be final, Bloomberg wrote.

Read alsoTrump: "It certainly looks like" Russia behind poisoning of ex-spy

Trump is prepared to act but wants to be sure European allies will take similar steps against Russia before doing so, aides said.

Deputy White House Press Secretary Raj Shah told Bloomberg on Saturday: "The United States stands firmly with the United Kingdom in condemning Russia's outrageous action. The president is always considering options to hold Russia accountable in response to its malign activities. We have no announcements at this time."

As UNIAN reported earlier, the United States and up to 20 European countries are preparing to expel Russian diplomats linked to Moscow espionage networks.