(Reuters) – U.S. and Iranian forces have exchanged heavy missile and drone assaults, with Tehran targeting U.S. facilities in states across the Gulf ​on Sunday and saying it had again closed the vital Strait of Hormuz.

The renewed violence casts further doubt on the future of an interim U.S.-Iranian agreement signed last month that aimed to ‌reopen the strait and end the war after a further 60 days of negotiations.

The strikes were the latest in a cycle of attacks and counter-attacks as Iran seeks to assert control over shipping through the Strait of Hormuz. However, the barrage marked an escalation in pace and range.