"The United States of America was not involved in the catastrophic accident during final launch preparations for the Safir SLV Launch at Semnan Launch Site One in Iran," Trump said in a tweet.

Publicly available satellite photos show what appears to have been the rocket's explosion on its launch pad.

Iran says its rocket program is for civilian use in space. However, because the rockets use similar technology to long-range ballistic missiles, Washington eyes the country's activities skeptically.

Washington and Tehran have been locked in a bitter standoff since last year when Trump unilaterally pulled out of the 2015 deal that gave Iran relief from sanctions in return for curbs on its nuclear program.

Iran says its atomic program is to develop nuclear power capabilities, but the United States, its ally Israel and Iran's other rivals in the region insist that this is a cover for a weapons push.

Tensions have risen dramatically in the Gulf, where Iran has seized tankers and the United States is expanding its military presence.