Russian Foreign Minister Sergei Lavrov said on Friday the risks of a military conflict over North Korea's nuclear program are very high, and Moscow is deeply worried by the mutual threats being traded by Washington and Pyongyang.

"Unfortunately, the rhetoric in Washington and Pyongyang is now starting to go over the top," Lavrov said. "We still hope and believe that common sense will prevail."

Asked at a forum for Russian students about the risks of the stand-off escalating into armed conflict, he said: "The risks are very high, especially taking into account the rhetoric."

"Direct threats of using force are heard... The talk (in Washington) is that there must be a preventive strike made on North Korea, while Pyongyang is threatening to carry out a missile strike on the U.S. base in Guam. These (threats) continue non-stop, and they worry us a lot."

"I won't get into guessing what happens 'if'. We will do whatever we can to prevent this 'if'."

"My personal opinion is that when you get close to the point of a fight breaking out, the side that is stronger and cleverer should take the first step away from the threshold of danger," said Lavrov, in remarks broadcast on state television.

He encouraged Pyongyang and Washington to sign up to a joint Russian-Chinese plan, under which North Korea would freeze its missile tests and the United States and South Korea would impose a moratorium on large-scale military exercises.

"If this double freezing finally takes place, then we can sit down and start from the very beginning - to sign a paper which will stress respect for the sovereignty of all those parties involved, including North Korea," Lavrov said.