Chuck Hagel, the US defence secretary, has ordered the US military to transport African troops from Burundi into the Central African Republic to help quell the latest upsurge in violence there.
Hagel approved the order after speaking with French Minister of Defence Jean-Yves Le Drian on Monday night from Afghanistan where he was visiting troops.
Le Drian asked the US to help get the troops quickly into the country to prevent the violence there from spreading, said Pentagon spokesman Carl Woog.
There are more than 1,000 French troops in the Central African Republic, where more than 400 people were killed in two days of violence last week between Christians and Muslims.
The fighting in the former French colony is between the mainly Muslim Seleka rebels - originally from neighbouring Chad and Sudan - and the Christian anti-Balaka whose name means "machete", the weapon of choice for Seleka.
The Christian fighters oppose the Muslim ex-rebels now in charge in the Central African Republic.
'A different path'
Woog said Hagel directed the US Africa Command to begin transporting forces in coordination with France because the US believes immediate action is needed to avert a humanitarian catastrophe.
He said the Pentagon will be evaluating what other US resources might be available if additional requests for assistance come in.
Hagel's order came hours before President Barack Obama recorded an audio message urging calm in the Central African Republic.
Obama taped the message on Monday in Dakar, Senegal, as Air Force One was refuelling on its way to South Africa for a memorial service honouring former President Nelson Mandela, who died last week.
Addressing his remarks to "the proud citizens of the Central African Republic," Obama said citizens have the power "to choose a different path" than violence.
Those who commit crimes should be arrested, Obama said, adding that the US will support the efforts of African countries and the French to restore security and protect civilians.
The transport flights are expected to begin in a day or two, according to a senior defence official who was not authorised to speak by name about the planning and thus requested anonymity.
The official said there would be no other US troops on the ground except any air crew needed for the flights into the Central African Republic.
Meanwhile, shooting erupted on Monday near the airport as the French troops searched for weapons in the capital Bangui, according to the Reuters news agency.
French forces later came under attack by former rebels in the city centre but there were no reports of casualties.
A top Seleka commander, Nourdine Adam, was taken into custody following the clashes.
"Nourdine Adam was taken into custody and transferred to the airport's international military base, after an altercation on a road with local residents," Al Jazeera's Nazanine Moshiri said on Monday. "He stayed there for a while, but he was later seen at the Presidential Palace."
"We don't know whether he was picked up by the French as part of their disarmament drive, or for his own safety," Moshiri added.
Source: Al Jazeera and agencies