The United States government on Tuesday imposed sanctions on two North Korean officials who, it says, led the country’s nuclear missile development programme, Reuters reported. The steps block access to any property or business interests that the two have in the US, and prohibit US citizens from dealing with them.

The US Treasury Department said one of the individuals, Kim Jong Sik, was a key figure in North Korea’s efforts to switch its missile programme from liquid to solid fuel. The other, Ri Pyong Chol, was a key official in Pyongyang’s Intercontinental Ballistic Missile programme, the US said.

“[The] Treasury is targeting leaders of North Korea’s ballistic missile programmes, as part of our maximum pressure campaign to isolate [Pyongyang] and achieve a fully denuclearised Korean Peninsula,” US Treasury Department Secretary Steven Mnuchin said.

Washington’s move comes days after the United Nations Security Council imposed new sanctions on North Korea for its nuclear and ballistic missile programmes. On Sunday, North Korea described the sanctions as an “act of war” and warned of action against the countries that supported them.

Russia offers to mediate

Meanwhile, Russia on Tuesday said it was ready to act as a mediator for talks between the US and North Korea if the two countries agreed. “Russia’s readiness to clear the way for de-escalation is obvious,” Kremlin spokesperson Dmitry Peskov told reporters.

Russia had made a similar offer of mediation on Monday. On Tuesday, Russian Foreign Minister Sergei Lavrov told US Secretary of State Rex Tillerson that “Washington’s aggressive rhetoric” and increased military presence in the Korean Peninsula had “heightened tensions” and was “unacceptable”.

Responding to the offer of mediation, US State Department spokesperson Justin Higgins said, “It is up to North Korea to change course and return to credible negotiations.”