Iran said it considers the Strait of Hormuz closed once again after a vessel using an ‘unauthorized route’ was struck by a warning shot in the critical waterway, further jeopardizing the already tenuous ceasefire agreement with the United States.

The White House and U.S. military officials offered no immediate comment on the closure, nor did they say whether American retaliation could be coming.

The announcement followed Iran and Oman’s foreign ministers meeting on Saturday to discuss the strait that lies between them, after days of Iranian attacks on ships and U.S. retaliation that dealt a blow to the interim deal to end the war.

Iran’s new supreme leader, still unseen since the war began, vowed in his first statement since the funeral of his father, Ayatollah Ali Khamenei that Iranians would avenge his killing in the war’s opening strikes on Feb. 28.

Such revenge “is the will of our nation and must certainly be carried out,” Supreme Leader Mojtaba Khamenei said in a statement carried on state television, hours after U.S. President Donald Trump threatened more missile attacks.