Russian ambassador to the U.S. Anatoly Antonov reiterated his country’s strong opposition to North Korea’s nuclear weapons and long-range missile programs on Monday, in comments that come as Moscow and Washington enter a new period of uncertainty in negotiations with Pyongyang.

The ambassador also said Russia would like to step up cooperation with the U.S. on the matter, while discussions on North Korea were held elsewhere between the U.S. and Russian foreign ministries in recent days as well.