Moscow, Jan 26 (IANS): Russia and the US have started expert-level work on the extension of the New Strategic Arms Reduction Treaty (New START), Russian Foreign Ministry spokesperson Maria Zakharova said on Monday.

"I can only say that experts are actively working in this direction. This is practical work and it has begun," Zakharova told a TV program.

Commenting on the future of Russian-US relations, the diplomat reiterated that the Donald Trump administration only complicated Washington-Moscow ties, which need to be mended in many spheres, the Xinhua news agency reported.

Also on Monday, Russian Security Council Secretary Nikolai Patrushev and US National Security Advisor Jake Sullivan held a phone conversation to discuss the extension of the New START and Russian-US cooperation in the field of security.

Presidential spokesman Dmitry Peskov said last week that the Kremlin welcomes the US proposal on a full five-year extension of the New START, but it is significant to take each other's concerns into consideration.

In 2010, Washington and Moscow signed the New START, which stipulates limits to the numbers of deployed nuclear warheads and strategic delivery systems by both.

The key pact, the last remaining nuclear arms control treaty in force between the two nuclear superpowers, will expire on Feb. 5.