TRIPOLI, Libya — The United States is discussing with the Libyan interim government the creation of a program to purchase shoulder-fired, heat-seeking missiles from militia members and others who gathered them up during the war, American government officials said.

The talks are the latest step in a multinational effort to contain the risks posed by the thousands of portable antiaircraft weapons that are unaccounted for after rebel fighters overran government weapons depots during the battle against Col. Muammar el-Qaddafi’s forces. Western security officials worry that terrorists could use this particular type of missile, which is lightweight and relatively easy to fire, to menace civilian passenger planes.

Details remain unresolved, the officials said. But in essence the United States would provide money and technical support to Libya’s government, which would purchase the missiles, and either lock them up in government arsenals or destroy them.

“We think we have come to the point where we need some sort of special program,” one official familiar with the plans said.