JOHANNESBURG — The US military has switched from trying to degrade Islamic extremist groups in West Africa’s sprawling Sahel region to merely trying to contain them, a new US government report says.

The quarterly report by the inspectors general for the Pentagon, State Department, and USAID released this week was the first one to be unclassified as interest surges in the US military’s activities in Africa. Security allies are worried as the United States considers cutting troops on the continent to counter China and Russia elsewhere in the world.

Top concerns in Africa include the fast-growing threat from multiple extremist groups in the Sahel region just south of the Sahara Desert and the enduring threat by the al-Qaida-linked al-Shabab in Somalia, which killed three Americans in an attack against US forces in Kenya last month.

Consistent pressure on extremist groups is needed to weaken them, the report says, citing Defense Secretary Mark Esper, who has compared it to “mowing the lawn.’’ That need, along with the often slow development of local partners’ militaries, “could require ongoing commitment of US military resources,’’ the report adds.

The new report says the US Africa Command has expressed concerns to the Pentagon’s inspector general that some resources will be moved from Somalia to the North African nation of Libya, where a conflict between rival governments has drawn the attention of powers, including Russia and Turkey.

About 6,000 US military personnel are deployed across Africa, the report says, including 500 special operations forces in Somalia and about 800 personnel in West Africa.

Extremist groups affiliated with the Islamic State group and al-Qaida in West Africa’s Sahel “are neither degraded nor contained,’’ the report warns, citing AFRICOM.