The Spanish government said on Friday it had approved an agreement to host a permanent force of 2,200 US Marines for deployment on missions to Africa.

Spain and the United States will formalise the deal by signing an amendment to a 1988 defence partnership during a visit by US Secretary of State John Kerry to Madrid on Monday.

Madrid agreed to permanently extend an agreement under which the force has been based at Moron de la Frontera, near Seville in southern Spain, said Deputy Prime Minister Soraya Saenz de Santamaria.

"The deployment at the Moron base will be made permanent with a force of 2,200 military personnel and 500 civilian staff plus 26 aircraft," she told a news conference.

The base will be able to host temporary extra deployments of up to 800 more personnel and 14 more planes, she said.

Currently 800-strong, the US force was first stationed at Moron in April 2013 after a deadly attack on the US consulate in Benghazi, Libya the previous year.

"The aim is to contribute to the stability of the region and common security in Africa, Europe and the Middle East," Saenz said.

From Moron the Marines will be able to launch missions in the region to protect their embassies or rescue other US personnel in difficulty, evacuate civilians or intervene in conflicts and humanitarian crises.

Among the aircraft to be deployed will be MV-22 Osprey transport planes that can take off vertically with big wing-mounted propellors.