Iran’s parliament may consider raising uranium enrichment to 90%, reaching weapons-grade levels, if the US resumes attacks, as the ceasefire between the two nations remains uncertain.

Iran's parliamentary national security and foreign policy commission spokesperson Ebrahim Rezaei warned that "one of Iran's options in the event of another attack could be 90% enrichment. We will review it in the parliament," The Caspian Post reports, citing The New Arab.

The warning on nuclear enrichment, a key part of the back-and-forth negotiations between Washington and Tehran, comes as Trump rejected what he called a "garbage" new proposal by the Iranians.

"I would call it the weakest right now, after reading that piece of garbage they sent us. I didn't even finish reading it," he said, warning that the ceasefire was "on life support".

Despite the ceasefire between the two sides that has largely stopped the bombing, which came into effect on 7 April, clashes have still occurred between the two sides, and traffic has yet to fully open through the vital Strait of Hormuz.