WASHINGTON — Secretary of State Rex Tilllerson called on African nations Friday to do more to isolate North Korea, which relies on trade and military relationships on the continent as a source of hard currency.

Speaking to African foreign ministers at the State Department, Tillerson said North Korea poses a threat to the world, not just Asia and the U.S. and that as such all countries have an obligation to reduce that threat.

“Let me stress that the United States seeks greater support from our African partners on growing global security matters, including North Korea,” he said.

Tillerson said the U.S. appreciated African condemnations of North Korean missile launches and nuclear tests and compliance with U.N. sanctions on Pyongyang. But, he said they should go beyond by downgrading diplomatic ties, severing economic links, expelling North Korean workers and reducing any other presence North Korea might have in their countries.

He urged all of Africa to play a part in what he has termed a “peaceful pressure campaign” to convince North Korea that its security and respect from the international community can only come from entering a “meaningful dialogue about a different future.”

As North Korea has faced increasing isolation from western countries, it has increasingly sought relationships with in Africa, the Middle East and South Asia to raise badly needed finances. 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.

The Trump administration has been pushing foreign countries to reduce economic, diplomatic and other ties to Pyongyang to further isolate it and bring it back to the negotiating table. In recent weeks, the administration has been targeting African and South Asian nations and some have agreed.

Tillerson’s comments came a day after Sudan pledged to Tillerson’s deputy, John Sullivan, that it would cut all of its military and trade ties with North Korea.

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 U.N. sanctions against Pyongyang. North Korea had for years trained Ugandan security forces in physical fitness, maritime warfare and weapons handling.