The United States and a number of EU member states will announce their decision to expel Russian diplomats as a response to a spy poisoning on British soil.

"Source:  Expecting a coordinated annoucement between US and multiple European countries tomorrow, expelling Russian diplos in droves. A "significant number" likely getting the boot," a CNN correspondent at covering the U.S. State Department, Michelle Kosinski, tweeted in the early hours of Monday.

As Bloomberg reported on Saturday, U.S. 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.

At the EU Foreign Affairs Council last week, European leaders agreed with the UK position that it is "highly likely" that Russia stands behind the Salisbury attack.

Read alsoBBC: Putin most likely behind spy poisoning – JohnsonAccording to media reports, Poland, Baltic states, and France could pass a decision to expel Russian diplomats.

Britain has already expelled 23 Russian diplomats and suspended high level diplomatic contacts with Russia.