WASHINGTON — The Trump administration warned on Thursday that a festering dispute between Qatar and its fellow Arab neighbors is at an impasse.

“We believe that this could potentially drag on for weeks. It could drag on for months. It could possibly even intensify,” said Heather Nauert, a spokeswoman for the State Department. And in a joint statement, Saudi Arabia, the United Arab Emirates, Egypt and Bahrain said Qatar “has worked to thwart the efforts and diplomatic efforts to resolve the crisis.”

The dispute among the mostly Sunni Muslim nations puts a host of top United States priorities at risk, including the effort to defeat the Islamic State and rebuild portions of Iraq and Syria that have been devastated by three years of fighting.

Riyadh, Abu Dhabi, Cairo and Manama last month announced an embargo against Qatar to punish Doha for what the four capitals called its support for terrorism. It was largely the work of the Saudi defense minister, Mohammed bin Salman, who was elevated several weeks later to become Saudi Arabia’s new crown prince, and revealed fissures within the Trump administration.