**A US missile defence test that simulated an attack from Iran has failed, the defence department says.**It said a sea-based radar system fault had meant a long-range defence missile had failed to intercept its target.
A recent Pentagon report said Iran posed a “significant” threat to the US and its allies in the Middle East.
The US is speeding up the deployment of defences in the Gulf to counter what is seen as the growing threat from Iran’s short- and medium-range missiles.
This includes deploying ships off the Iranian coast and Patriot anti-missile systems in several Gulf countries.
In the exercise on Sunday, a target missile was fired from Kwajalein in the Marshall Islands, and the interceptor from Vandenberg Air Force base in California.
“The Sea-Based X-band radar did not perform as expected”
Missile Defense Agency
Both had performed normally, the Missile Defense Agency said.
“However, the Sea-Based X-band radar did not perform as expected,” the agency said on its website.
Officials would investigate the cause of the failed $150m (£94m) test, it said.
Previous US missile defence tests have imitated an attack from North Korea, but this was the first time a flight path from Iran was used.
It comes as the impasse over Tehran’s nuclear activities continues and the US steps up its deployment of anti-missile capabilities in the Gulf.
However, correspondents say the moves are more of a defensive manoeuvre against Iran than an aggressive one.