NEW YORK, March 26 (Xinhua) -- The U.S. decision to expel Russian diplomats is a "very unfortunate and very unfriendly move," Russian Ambassador to the United Nations (UN) Vassily Nebenzia said Monday.

The 60 Russian diplomats to be expelled include 12 members of Nebenzia's delegation to the UN.

"It is very unfortunate and very unfriendly move. We were informed that 12 diplomats from the Russian mission to the UN are expelled from here and they have to leave by April 2," Nebenzia told reporters before a luncheon of the Security Council with UN Secretary-General Antonio Guterres.

Both Nebenzia and U.S. ambassador Nikki Haley were present.

Nebenzia said the 12 diplomats are leaving the United States.

He refused to name the diplomats. "We don't name those diplomats. We safeguard their privacy," he said.

Earlier on Monday, Haley said her country has begun the process of "expelling 12 intelligence operatives from the Russian Mission to the United Nations who have abused their privilege of residence in the United States."

"After a review, we have determined that the 12 intelligence operatives engaged in espionage activities that are adverse to our national security. Our actions are consistent with the United Nations Headquarters Agreement," said Haley in a press statement.

Asked whether the U.S. decision is in accordance with the UN-U.S. agreement on the UN Headquarters in New York, Nebenzia said: "I don't think so."

The U.S. expulsion is said to show solidarity with its ally Britain, which claims that Moscow is responsible for the poisoning of a former Russian spy on March 4 in Britain with a military-grade nerve agent.

Russia has denied involvement in the case.