MOSCOW, Dec. 27 (Xinhua) -- Russian Foreign Minister Sergei Lavrov told U.S. Secretary of State Rex Tillerson Tuesday it is "inadmissible" that Washington heightened tension on the Korean Peninsula with "aggressive rhetoric" and military buildup.

Lavrov made the remarks during a phone conversation with Tillerson, according to a press release of the Russian Foreign Ministry.

The two sides believe that Pyongyang's nuclear missile development violated the requirements of the United Nations Security Council, it said, underscoring the need for "an early transition from words of sanctions to a negotiation process."

During the phone call, the two top diplomats also considered steps to overcome the conflicts in Syria while maintaining its territorial integrity, including the plan to hold an inter-Syrian national dialogue in Russia's Sochi.

They also agreed to intensify dialogue on issues concerning strategic stability and to remain in close contact.