Qatar is sending its ambassador back to Iran, a move that risks inflaming a diplomatic standoff between the tiny Gulf nation and a Saudi-led bloc of Arab neighbors just as the U.S. steps up attempts to heal the rift, WSJ reported.

The move appeared aimed at signaling Qatar’s displeasure with Saudi Arabia over the standoff, which began when Riyadh and three other nations severed ties with Doha in early June to protest its close relations with Tehran and its alleged support for regional extremist groups. Qatar denies the allegations.

Doha’s decision threatens Washington’s efforts to resolve the dispute between pivotal Mideast allies. Qatar is home to a base from which the U.S. oversees the military campaign against Islamic State. On Saudi Arabia’s side are the United Arab Emirates, Egypt and Bahrain, where the U.S. Navy’s Fifth Fleet is based.

Washington has emphasized trying to ease tensions and bring the feud to an end, and officials urged calm on Thursday. “We really want all sides to exercise restraint and to really tone down the rhetoric because it’s not helpful and it’s not leading to any productive conversations,” a State Department official said.