Diplomacy with Iran must be backed up by US military might, Pentagon chief Chuck Hagel said yesterday in a speech addressed to Gulf allies anxious over a nuclear deal with Tehran. Hagel promised the United States would maintain a 35,000-strong force in the Gulf region, as well as an armada of ships and warplanes, despite the recent deal with Tehran. Speaking at a security conference in Bahrain, he said the interim deal with Iran to roll back its nuclear programme was a risk worth taking but that Western diplomacy should not be misinterpreted. "We know diplomacy cannot operate in a vacuum," he said. "Our success will continue to hinge on America's military power, and the credibility of our assurances to our allies and partners in the Middle East." The Pentagon "will not make any adjustments to its forces in the region - or to its military planning - as a result of the interim agreement with Iran", Hagel added. In a trip meant to reassure Gulf allies wary of America's diplomatic opening with Iran, he enumerated an array of US weaponry and resources deployed in the region. The military footprint includes 10,000 US army troops with tanks and Apache helicopters, roughly 40 ships at sea including an aircraft carrier battle group, missile defence systems, radar, surveillance drones and warplanes that can strike at short notice, he said. "Coupled with our unique munitions, no target is beyond our reach," said Hagel, in an apparent reference to "bunker buster" bombs designed to penetrate deeply buried targets. A senior US defence official, who spoke on condition of anonymity, said the speech sent a message of solidarity to Gulf allies while also conveying a warning to adversaries "that any sort of mythology of American retreat is just wrong-headed". Gulf allies, especially Saudi Arabia, are concerned over a November 24 interim accord between world powers and Iran that offers limited relief from Western sanctions in return for Tehran rolling back elements of its nuclear programme.