The United States announced sanctions on two North Korean officials behind their country’s ballistic missile programme on Tuesday, while Russia reiterated an offer to mediate to ease tensions between Washington and Pyongyang.

The new US steps were the latest in a campaign aimed at forcing North Korea — which has defied years of multilateral and bilateral sanctions — to abandon a weapons program aimed at developing nuclear-tipped missiles capable of hitting the United States.

The US Treasury named the officials as Kim Jong Sik and Ri Pyong Chol. It said Kim was reportedly a key figure in North Korea’s efforts to switch its missile programme from liquid to solid fuel, while Ri was reported to be a key official in its intercontinental ballistic missile (ICBM) development.

“Treasury is targeting leaders of North Korea’s ballistic missile programs, as part of our maximum pressure campaign to isolate (North Korea) and achieve a fully denuclearized Korean Peninsula,” Treasury Secretary Steven Mnuchin said in a statement.

The move followed new United Nations sanctions announced last Friday in response to North Korea’s Nov. 29 test of an ICBM that Pyongyang said put all the US mainland within range of its nuclear weapons. Those sanctions sought to further limit North Korea’s access to refined petroleum products and crude oil and its earnings from workers abroad.

North Korea declared the UN steps to be an act of war and tantamount to a complete economic blockade.

North Korea announces intercontinental missile launch Show all 13 1 /13 North Korea announces intercontinental missile launch North Korea announces intercontinental missile launch Pyongyang residents react after the news of the successful launch of the new intercontinental ballistic missile AFP/Getty Images North Korea announces intercontinental missile launch North Korea's leader Kim Jong Un signing an order to test-fire the newly developed inter-continental ballistic missile KRT via AP Video North Korea announces intercontinental missile launch A news broadcast displays Kim Jong Un's signed document AP North Korea announces intercontinental missile launch People cheer as they watch the news broadcast announcing Kim Jong Un's order to test-fire the new inter-continental ballistic missile AFP/Getty Images North Korea announces intercontinental missile launch Residents react after the document signing AP North Korea announces intercontinental missile launch Pyongyang residents celebrate Kim Jong Un's announcement AFP/Getty North Korea announces intercontinental missile launch Cheering Pyongyang residents react AP North Korea announces intercontinental missile launch To counter North Korea's missile test, South Korea fired missiles into the East Sea The Defence Ministry/Yonhap via REUTERS North Korea announces intercontinental missile launch The Hyunmu-2 missiles firing during the drill South Korean Defense Ministry vi North Korea announces intercontinental missile launch The exercise was carried out in an attempt to counter Kim Jong Un's order South Korea Defense Ministry via AP North Korea announces intercontinental missile launch The South Korean army continue to carry out military exercises AP North Korea announces intercontinental missile launch Where K-9 self-propelled howitzers were taking part in a drill Rex Features North Korea announces intercontinental missile launch US soldiers are also present in the border city of Paju AFP/Getty Images

The standoff between the United States and North Korea has raised fears of a new conflict on the Korean peninsula, which has remained in a technical state of war since the 1950-53 Korean War ended in an armistice not a peace treaty.

Washington has said that all options, including military ones, are on the table in dealing with North Korea. It says it prefers a diplomatic solution, but that North Korea has given no indication it is willing to discuss denuclearisation.

On Tuesday, the Kremlin, which has long called for the two sides to hold negotiations, said it was ready to act as a mediator if the United States and North Korea were willing for it to play such a role.

“Russia’s readiness to clear the way for de-escalation is obvious,” Kremlin spokesman Dmitry Peskov told reporters.

UN security council unanimously agrees new sanctions for North Korea

The US State Department and White House did not immediately respond to a request for comment on Moscow’s offer.

Russian Foreign Minister Sergei Lavrov, who made a similar offer on Monday, told US Secretary of State Rex Tillerson in a phone call on Tuesday that “Washington’s aggressive rhetoric” and beefing up of its military presence in the region had heightened tensions and was unacceptable, Russia’s foreign ministry said.

It said Lavrov underscored the need for “the fastest move to the negotiating process from the language of sanctions.”

Washington has stressed the need for all countries, especially Russia, and China — North Korea’s main trading partner — to fully implement sanctions, including by cutting off oil supplies.

According to Chinese customs data, China exported no oil products to North Korea in November, apparently going above and beyond UN sanctions imposed earlier this year.

Beijing also imported no North Korean iron ore, coal or lead in November, the second full month of those trade sanctions, the data showed.

Beijing has not disclosed its crude exports to North Korea for several years, but industry sources say it still supplies about 520,000 tonnes, or 3.8 million barrels, a year to the country via an aging pipeline.

North Korea also sources some of its oil from Russia.

Trade between North Korea and China has slowed through the year, particularly after China banned coal purchases in February.

Chinese exports of corn to North Korean in November also slumped, down 82 per cent from a year earlier to 100 tonnes, the lowest since January. Exports of rice plunged 64 per cent to 672 tonnes, the lowest since March.

China has expressed concern about the humanitarian effects of sanctions, and has repeatedly called for constructive efforts to ease tensions.