Russian Foreign Minister Sergei Lavrov says he is "united in opinion" with his U.S. counterpart Rex Tillerson on the issue of North Korea but that they differ on how to resolve the crisis over Pyongyang's nuclear weapons program.

The two diplomats spoke by phone on December 26 and "shared a common opinion that the nuclear-missile developments in [North Korea] violate the demands of the United Nations Security Council," according to a statement from the Russian Foreign Ministry.

Lavrov disagreed with U.S. threats of military intervention and further sanctions against North Korea, instead pushing for U.S. diplomacy to seek a more peaceful approach to negotiations, the statement said.

"The importance of an early transition from the language of sanctions to negotiations was emphasized," the statement outlining the conversation said.

Also on December 26, the United States placed sanctions on two senior North Korean officials over Pyongyang's ballistic missile program.

The Treasury Department named the two as Kim Jong Sik, thought to be a key figure in North Korea's efforts to switch its missile program from liquid to solid fuel, and Ri Pyong Chol, who is believed to be a key official involved in the country's intercontinental ballistic missile development.

On December 22, the UN Security Council unanimously approved new sanctions on North Korea in response to last month's launch of a ballistic missile that Pyongyang says is capable of reaching anywhere on the U.S. mainland.

The new sanctions include sharply cutting limits on North Korea's imports of refined oil and orders the repatriation of all North Korean nationals working abroad by the end of 2019.

Kremlin spokesman Dmitry Peskov told reporters on December 26 that Moscow was willing to act as a mediator in the row "if both sides need it and want it."

At a UN meeting earlier this month, Tillerson chastised Russia and China for their ties to Pyongyang, saying Moscow's use of North Korean labor and China's supply of oil to the country undermined international sanctions efforts.

The sanctions are aimed at choking off external sources of funding for North Korea's nuclear weapons and ballistic-missile development programs after repeated tests this year have brought the Asian nation to what experts say is the brink of developing devastating weapons that can be delivered halfway around the world.