India, Sept. 17 -- Saudi Arabia accused Yemen's Iran-backed Houthi rebels of trying to attack Islam's holiest city, as the region responded with condemnation Wednesday but no sign of military support. The kingdom, a key US ally, declared Mecca a "red line" as it slid deeper into the new front of the Iran war.

With the world's biggest oil exporter under fire from the rebels backed by the Saudis' regional adversary, the kingdom needs a safe outlet for its crude as well as military assistance. There's no clear path to either.

A crucial Saudi pipeline has been shut down, reportedly for weeks, after an attack by Iranian-backed militias in Iraq. The Houthis have been targeting infrastructure in the kingdom and its shipping on the Red Sea, whe...