NEW YORK — Iran’s foreign minister on Wednesday ruled out cooperating with the United States in helping Iraq fight Islamic State militants and warned that the terrorist group poses a much broader global threat that needs new thinking to eradicate.

Mohammad Javad Zarif said Iran has serious doubts about the willingness and ability of the United States to react seriously to the “menace” from the Islamic State group “across the board” and not just pick and choose where to confront it as it has just started doing in Iraq.

“This is a very mobile organization,” he told the Council on Foreign Relations. “This is not a threat against a single community nor a threat against a single region. It was not confined to Syria, nor will it be confined to Iraq. It is a global threat.”

The U.S.-Iranian relationship is at a delicate moment, with a new round of talks on a deal to rein in Iran’s nuclear program set to begin on Thursday, which Zarif said is his top priority. Leaders of the two countries — who talked a year ago — are also arriving next week for the annual ministerial meeting of the U.N. General Assembly.

Iran was the first country to provide help to neighboring Iraq when the Islamic State group swept across the border from Syria in July.