The US military will help fly African Union peacekeeping troops to the Central African Republic as part of a French-led effort to restore security there, US officials said Monday.

Defense Secretary Chuck Hagel, in Qatar on a tour of the region, has ordered American forces "to begin transporting forces from Burundi to the Central African Republic, in coordination with France," his spokesman said in a statement.

The Pentagon will make two C-17 transport planes available to transport roughly 850 Burundian soldiers, a US defense official said on condition of anonymity, noting: "We hope to start tomorrow."

The mission to ferry the troops and their equipment should be completed in a matter of days, the official said.

Hagel took the decision after conferring by phone Sunday with French Defense Minister Jean-Yves Le Drian, who requested "limited" US military assistance to support the international effort, spokesman Carl Woog said.

"In the near term, France has requested airlift support to enable African forces to deploy promptly to prevent the further spread of sectarian violence in the Central African Republic," he said.

"The United States is joining the international community in this effort because of our belief that immediate action is required to avert a humanitarian and human rights catastrophe in the Central African Republic, and because of our interest in peace and security in the region."

Meanwhile US President Barack Obama appealed for calm in the country and for the arrests of those behind the surge of sectarian violence, the White House said.

Deputy national security advisor Ben Rhodes told reporters on Air Force One Obama recorded the message to the country while on a refueling stop in Dakar on his way to South Africa for Nelson Mandela's memorial.

"The awful violence of recent days threatens the country you love," Obama said, urging people to "choose a different path."

Muslim and Christian leaders "are calling for calm and peace. I call on the transitional government to join these voices and to arrest those who are committing crimes," Obama said.

The United States would look to possibly provide "additional resources" if needed, the military statement said, without offering details.

More than a year ago, the United States deployed about 100 special forces to the region to help Ugandan forces track warlord Joseph Kony and his Lord's Resistance Army (LRA) fighters.

The US troops are based in Uganda, but their search involves a stretch of jungle in the eastern corner of the Central African Republic.

The announcement from the Pentagon came as French troops on Monday started disarming fighters in the country after a spike in sectarian violence that claimed hundreds of lives.

In addition to the French contingent on the ground, the African Union plans to bolster a regional force to 6,000 troops from an initially planned 3,600.

The Pentagon offered similar assistance during the French intervention in Mali, providing cargo aircraft and sharing intelligence with their allies.