As part of their attempts to avoid being caught in the crossfire, Gulf states including Saudi Arabia, the United Arab Emirates and Qatar are also refusing to let Israel fly over their airspace for any attack on Iran and have conveyed this to Washington, the three sources close to government circles said.

The moves by the Gulf states come after a diplomatic push by non-Arab Shi'ite Iran to persuade its Sunni Gulf neighbours to use their influence with Washington amid rising concerns Israel could target Iran's oil production facilities.

During meetings this week, Iran warned Saudi Arabia it could not guarantee the safety of the Gulf kingdom's oil facilities if Israel were given any assistance in carrying out an attack, a senior Iranian official and an Iranian diplomat told Reuters.