US President Donald Trump is weighing options against Iran that include targeted strikes on security forces and leaders to inspire protesters, multiple sources said, even as Israeli and Arab officials said air power alone would not topple the clerical rulers.

Two US sources familiar with the discussions said Trump wanted to create conditions for "regime change" after a crackdown crushed a nationwide protest movement earlier this month, killing thousands of people.

To do so, he was looking at options to hit commanders and institutions Washington holds responsible for the violence, to give protesters the confidence that they could overrun government and security buildings, they said.

Trump has not yet made a final decision on a course of action including whether to take the military path, one of the sources and a US official said.

The second US source said the options being discussed by Trump's aides also included a much larger strike intended to have lasting impact, possibly against the ballistic missiles that can reach US allies in the Middle East or its nuclear enrichment programmes.

Iran has been unwilling to negotiate restrictions on the missiles, which it sees as its only deterrence against Israel, the first source said.