But their staunchest ally, the United States, opposes the move, as do Iraqi rivals and regional powers. They say it could spark new conflicts and aggravate old ones at a time when the nation is on the cusp of defeating the Islamic State.

Kurdish officials pushing the Sept. 25 referendum say there is no need to panic. The poll, which is widely expected to result in a resounding vote to secede from Iraq, is simply an important first step in what would be a lengthy but amicable divorce from the Iraqi state, they say.

“We will ourselves not initiate a clash or a fight,” said Rowsch Shaways, a former deputy prime minister of Iraq and the head of the Kurdish delegation negotiating with Baghdad. “We are pledging dialogue and a peaceful solution.”