Government efforts to revive by next month stalled negotiations with the country's biggest communist insurgent group, the National Democratic Front (NDF), are facing another setback after the rebels expressed opposition to the presence of American troops in the country.

"The peace talks are not only being delayed, but are now in danger of collapsing due to the shameless violation of national sovereignty after the government allowed armed intervention by U.S. troops in the Philippines," said Gregorio Rosal, chief of the NDF's armed wing, the New Peoples' Army.

More than 660 American soldiers are now in southern Philippines taking part in joint exercises with their Filipino counterparts.

Both Manila and Washington have said that the war drills are aimed at training local soldiers in combating the extremist Abu Sayyaf and are not intended to neutralise other rebel groups such as the NPA and the secessionist Moro Islamic Liberation Front (MILF).

But despite the government's assurance, the NDF and the NPA remained apprehensive.

"Our self-restraint not to end the peace talks is nearing its limits," said Rosal.

He added that it is likely that American troops could join Filipino soldiers in operations against them since the NPA is also considered a "terrorist" group by the United States.