Several key U.S. allies on Sunday called for renewed diplomacy after American strikes on Iran raised fears of broader conflict, while regional players – including Tehran's backers – condemned the attacks but also urged deescalation.

U.S. President Donald Trump had said Thursday that he would decide within two weeks whether to get involved in Israel's war with Tehran. In the end, it took just days. Washington hit three Iranian nuclear sites early Sunday.

While the amount of damage remained unclear, Iranian Foreign Minister Abbas Araghchi said the U.S. had "crossed a very big red line," the time for diplomacy was over and Iran had the right to defend itself.

Some have questioned whether a weakened Iran would capitulate or remain defiant and begin striking with allies at U.S. targets scattered across the Gulf region.

U.N. Secretary-General Antonio Guterres said he was "gravely alarmed" by the use of force by the United States.