PARIS — Iran and a group of six world powers completed a deal on Sunday that will temporarily freeze much of Tehran’s nuclear program starting next Monday, Jan. 20, in exchange for limited relief from Western economic sanctions.

The main elements of the deal, which is to last for six months, were announced in November. But its implementation was delayed as negotiators worked out technical details.

The agreement faced opposition from Iranian hard-liners and Israeli leaders, as well as heavy criticism from some American lawmakers, who have threatened to approve further sanctions despite President Obama’s promise of a veto.

It comes as Tehran has sought to expand its influence in the Middle East by providing weapons and sometimes members of its own paramilitary Quds Force, in what Western nations view as destabilizing activities in countries including Syria, Bahrain and Yemen, according to interviews with intelligence, military, diplomatic and government officials. However, both the United States and Iran have sought to insulate the nuclear negotiations from the tensions over Iran’s regional policies.