MOSCOW - Russia wants to know the evidence behind US accusations that Iran was behind an alleged plot to kill the Saudi ambassador in Washington before taking a position on the matter, Foreign Minister Sergei Lavrov said on Monday.

The Interfax news agency quoted Lavrov as saying the United States was sending representatives to discuss the allegations with Russia, which has ties with Iran and holds veto power as a permanent UN Security Council member.

"Experts will come to tell us about the situation. They have either been sent or are about to be sent. We have not heard them yet, and moreover, we are not going to say anything until we do," Interfax quoted Lavrov as saying.

US President Barack Obama has said Iran will face the harshest possible sanctions for the alleged plot and has not ruled out military action.  

UN Secretary-General Ban Ki-moon said on Monday that he had received correspondence from the United States, Iran and Saudi Arabia to the Security Council.

Russia has reluctantly supported four rounds of Security Council sanctions against Iran over its nuclear programme, but has repeatedly said it opposes additional sanctions.

The United States said last Tuesday it had uncovered a plot by two men with links to Iran's security forces to assassinate the Saudi envoy by planting a bomb in a Washington restaurant. The Iranian government denies any involvement.

In a statement on Wednesday, the Russian Foreign Ministry expressed concern over the reports and emphasised its opposition to "terrorism" but said nothing specific about its position on the allegations.