New Delhi, July 7 -- A tanker traveling off the coast of Oman in the Strait of Hormuz caught on fire early Tuesday morning after being struck by a projectile, the British military said.

The attack was the latest targeting a vessel moving through the narrow mouth of the Persian Gulf, through which a fifth of all oil and natural gas traded once passed in peacetime. Iranian state television said the liquefied natural gas tanker came under attack after ignoring warnings but did not directly claim the assault.

Tehran has repeatedly declared that only its approved route through the strait is safe and is suspected of attacking other ships that have used another route close to the Omani shore.

The U.S. is eager to press ahead with negotiations...