Yemen's Iran-aligned Houthis said on Monday they ​would impose a naval blockade on Saudi Arabia, opening a potential new front against the United States in its war with Iran and raising the threat to global energy supplies and trade beyond the Gulf, Reuters reported. 

The escalation comes after one of the deadliest periods in the war for U.S. troops. The Pentagon on Monday identified two U.S. soldiers who were killed when Iran attacked an American base in Jordan on Friday, while they also said they had found unidentified remains that could be those of a third soldier reported as missing in action.

Separately, a fourth service member was killed in northern Iraq during the "controlled detonation of unexploded ordnance from a downed Iranian one-way attack drone."