The United States and up to 20 European countries are preparing to expel Russian diplomats linked to Moscow espionage networks.

Read alsoFive EU member states considering expulsion of Russian diplomats – media

The unprecedented co-ordinated action will begin on Monday with the recall of the European Union's ambassador to Moscow for four weeks, according to The Times.

President Trump's National Security Council recommended last night that a yet-to-be determined number of Russian diplomats be expelled from the U.S. in response to the Salisbury attack. Mr. Trump is expected to take a final decision next week.