WASHINGTON (Reuters) - The United States on Tuesday announced sanctions on two North Korean officials for their roles in developing the country’s ballistic missiles, the latest step in a campaign to press Pyongyang to give up its nuclear and missile programs.

The U.S. 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 program from liquid to solid fuel, while Ri was reported to be a key official involved in the country’s 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.

“These actions follow Friday’s United Nations Security Council Resolution, which imposed strong new sanctions on North Korea further shutting down its ability to raise illicit funds.”

The U.N. Security Council imposed new sanctions on North Korea last week over a recent ICBM test. The sanctions sought to limit the country’s access to refined petroleum products and crude oil and its earnings from workers abroad.

North Korea, which has been working to develop nuclear-tipped missiles capable of hitting the United States, declared those steps to be an act of war and tantamount to a complete economic blockade against the country.