REUTERS, Singapore

Oil ​prices extended gains on Tuesday as a US-imposed deadline loomed for Iran to open the Strait of Hormuz or be “taken ‌out”, with US President Donald Trump threatening to order attacks on Iranian bridges and power plants.

Brent crude futures rose $1.44, or 1.3 percent, to $111.21 a barrel by 0700 GMT, while US West Texas Intermediate crude futures were up $2.32, or 2.1 percent, at $114.73.

Trump has threatened to rain “hell” on Tehran if it fails to comply with his deadline of 8 p.m. ​EDT on Tuesday (0000 GMT Wednesday) to reopen the strait, through which about a fifth of global oil supply is normally shipped, if a ​deal is not reached.

Responding to a US proposal through mediator Pakistan, Tehran rejected a ceasefire and said a permanent end to the war was necessary, and pushed back against pressure to reopen the strait.

Iran’s rejection of the US ceasefire proposal has kept tensions ​elevated and left diplomacy hanging by a thread, said Priyanka Sachdeva, senior market analyst at Phillip Nova.

“Oil is holding its gains because the ​battlefield risk is no longer theoretical. Attacks on energy and shipping assets continue, and traders fear that even if the war ends, damage to infrastructure could sideline barrels for months, not days,” she said.

Exports from several Gulf producers have already collapsed due to restricted flows through the Strait of Hormuz.

Iranian forces effectively shut the ​strait after US and Israeli attacks began on February 28.

“Clock-watching is now playing almost as big a role in oil markets as the ​fundamentals The