The country's leaders made their appeal for assistance on Thursday after rebels captured the town of Birao on Monday.
CAR officials said the rebels attacked from Sudan, leading to fears that the long-running conflict in Sudan's western Darfur region could further de-stabilise the region.
Francois Bozize, the president of the CAR, on Wednesday cut short his visit to an Africa-China summit in Beijing to deal with the threat posed by the rebels, who are demanding he agrees to talks on power sharing.
The UFDR, the anti-Bozize rebel coalition which has claimed the capture of Birao, said it was waiting to see whether the government would launch a counterattack to try to retake the town, or agree to talks.
"We'll be staying in Birao," UFDR spokesman captain Abakar Sabone told Reuters by telephone, "what we want is a round table to discuss sharing power, without exclusions."
The CAR, a former French colony and one of the poorest nations on earth, has accused neighbour Sudan of arming and directing the rebels.
The Sudanese government on Wednesday rejected the accusation.
Sudan role questioned
The CAR government said that France and regional allies like Chad, which has also accused Khartoum of backing rebel incursions from Darfur, had offered their support.
But Cyriaque Gonda, the president's spokesman said that the CAR government wanted "concrete aid" from the international community.
"Concretely, we want the positioning of (international peacekeeping) troops in the region," Gonda said.
The UN has already begun an emergency aid service to the rebel-held town where UN representatives and members of international aid organisation have now begun planning their response to the crisis.
Gonda declined to say what action the government intended to take against the rebels in Birao, which is located in a remote, rugged region of bush and marshland more than 800 km (500 miles) northeast of Bangui, the capital.