WASHINGTON-- US President Donald Trump said he has canceled scheduled strikes and bombings against Iran on Thursday evening, citing progress in ongoing negotiations.

"Based on the fact that discussions with the Islamic Republic of Iran have been brought to the highest level of Iranian leadership and approved, I have, as President of the United States of America, cancelled the scheduled strikes and bombings against Iran this evening," Trump wrote on Truth Social.

"Discussions and final points have been, in both concept and great detail, approved by all parties involved, including the United States, Israel, Saudi Arabia, UAE, Qatar, Turkey, Pakistan, Bahrain, Kuwait, Jordan, Egypt, and others," Trump said.

But the president noted that the US naval blockade will "remain in full force and effect" until a transaction is finalized, adding that time and place of the signing will be announced shortly.

Earlier on Thursday, Trump vowed to launch "bigger, more powerful" strikes against Iran later that night and take control of Kharg Island, which manages over 90 percent of Iran's oil exports.

So far, Iran has approved no draft for a preliminary memorandum of understanding with the United States on ending the war, the semi-official Fars news agency reported Thursday, citing an informed source close to the Iranian negotiating team.

Since a ceasefire between the United States and Iran took effect in early April, Trump has repeatedly expressed optimism that a peace agreement was within reach. However, no breakthrough has emerged so far.

US forces struck multiple Iranian targets in the past two days, in retaliation for Monday's downing of a US Army helicopter allegedly by an Iranian drone near the Strait of Hormuz.

The New York Times reported Thursday that based on its analysis of satellite images, it appeared that one US strike had hit a drinking-water facility, which could constitute a war crime.

A spokesman for the US military said it was investigating, said the report.

The Iranian Foreign Ministry said Thursday that fresh US strikes on Iran have effectively rendered the April ceasefire between the two countries "meaningless."