By JOHN J. LUMPKIN, Associated Press Writer

 WASHINGTON – U.S. Marines who killed two Haitians in separate incidents were acting within their orders to fire when they felt threatened, Pentagon (news – web sites) officials said Tuesday.

 U.S. forces in Haiti have a limited set of circumstances during which they are allowed to use deadly force. They cannot shoot to deter looters, even if the target of the looting is an American company.

 Officials have described the Marines’ mission as protecting crucial sites, such as government buildings and the airport, to facilitate the eventual arrival of a U.N. peacekeeping force. That mission expanded Tuesday, when Marines said they will begin helping Haitian police disarm rebel groups that have been threatening new violence.

 Late Monday, Marines shot and killed the driver of a vehicle speeding toward a military checkpoint, a spokesman said, the second person reported killed by the peacekeepers.

“When you see a vehicle approaching at high speed, it is seen as a threat so the Marines opened fire,” spokesman Sgt. Timothy Edwards said. A passenger was wounded.

 Marine Gen. Peter Pace, vice chairman of the Joint Chiefs of Staff, told reporters at the Pentagon that the Marines’ actions were “well within the rules of engagement. An individual Marine … has an absolute right to defend himself and those around him. When someone threatens force, as was done last night, then they get dealt with as they were dealt with last night.”

 Some officials have refused to be specific about the Marines’ rules of engagement to avoid giving militants or criminals guidance on what they may do without having a run-in with the international forces.

 Those rules are not expected to change absent a major change in the situation in Haiti, officials said.

 About 1,600 U.S. troops, mostly Marines, are in Haiti, and the number is not expected to grow significantly, said one Pentagon official, speaking on condition of anonymity. France, Chile and Canada have contributed another 700 soldiers, officials said.

 Pace said the 1,600 troops were within the 1,500 to 2,000 range previously provided by the Pentagon. He said more would be sent if requested by Gen. James T. Hill, commander of the Miami-based Southern Command.

 “I am very comfortable that the force on the ground right now is a force that General Hill needs,” Pace said. Marines said they shot and killed a gunman who fired at them during a demonstration Sunday in which seven people died, including a foreign journalist, and more than 30 were wounded.

Also Tuesday, CIA (news – web sites) Director George J. Tenet warned that in Haiti, “a humanitarian disaster or mass migration remains possible.”

 “A cycle of clashes and revenge killings could easily be set off, given the large number of angry, well-armed people on both sides. Improving security will require the difficult task of disarming armed groups and augmenting and retraining a national security force,” Tenet told the Senate Armed Services Committee (news – web sites).

 The sides are groups of militants that support and oppose exiled President Jean-Bertrand Aristide and some criminals.

 The toll from a monthlong rebellion and reprisal killings rose to more than 300, with the Pan-American Health Organization reporting an estimated 200 corpses at the state morgue as being victims of the violence.