BAGHDAD  Iraq’s foreign minister said Tuesday that the United States had agreed to lift immunity for foreign security contractors operating in Iraq, making them subject to prosecution under Iraqi law, according to Iraqi politicians.

In a briefing for lawmakers on the status of a complex security agreement being negotiated with the United States, the foreign minister, Hoshyar Zebari, said Iraq had insisted on ending the immunity for private security companies, according to three Iraqi politicians who were present. American troops are operating under a United Nations mandate that expires in December.

The private security companies, like Blackwater Worldwide, have reputations of using excessive force in protecting diplomatic and other foreign clients, and currently enjoy immunity from Iraqi law. That immunity became a political issue last fall, after a Blackwater shooting in Baghdad in September left 17 Iraqis dead, according to Iraqi investigators.

According to the three Iraqi politicians who were interviewed, Mr. Zebari said the agreement by the United States to lift the immunity eliminated one of many sticking points in the negotiations, which the United States has said it wants to complete by the end of this month.