State Department spokeswoman Heather Nauert said Sudan is taking the step due to the "critical threat" posed by the North's nuclear program.
She said the United States welcomed the decision, which was announced after a visit to Khartoum by Deputy Secretary of State John Sullivan. That visit came as the US and Sudan, encouraged by Israel and Saudi Arabia, moved to improve ties after decades of hostility.
The Trump administration has been pushing foreign countries to reduce economic, diplomatic and other ties to Pyongyang in an effort to further isolate the country and bring it back to the negotiating table.
In recent weeks, the administration has been targeting African and South Asian nations and several have agreed. Sudan has been a particular focus of the effort as part of an attempt to improve ties between Washington and Khartoum that has led to a lifting of some US sanctions against Sudan.
In Africa, it has cultivated military and economic ties with a number of countries, including Sudan, Uganda and Angola, that range from military training programs to construction and industrial projects and the supply of guest workers.
Last month, Uganda announced it had expelled North Korean military experts and representatives of North Korean companies, including its top arms dealer, as part of efforts to comply with new UN sanctions against Pyongyang. North Korea had for years trained Ugandan security forces in physical fitness, maritime warfare and weapons handling.