By Nayera Abdallah, Eman Abouhassira and Timour AzhariDUBAI/RIYADH, July 20 (Reuters) - 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.The Houthis made their announcement despite signs that Tehran and Washington want to resume diplomacy to halt a worsening cycle of attacks that has all but wrecked a fragile interim agreement signed last month.

Iran’s president says country is fighting a “full-scale war” with the US;

The Houthis fired missiles at Saudi Arabia last week after accusing the kingdom of bombing an airport under their control, breaking a four-year truce between the kingdom and the…