WASHINGTON (Reuters) - A maiden US attempt to shoot down a ballistic missile mimicking an attack from Iran failed after a malfunction in a radar built by Raytheon Co, the Defence Department said. The Missile Defence Agency said both the target missile, fired from Kwajalein in the Marshall Islands, and the interceptor, from Vandenberg Air Force Base in California, had performed normally after launch on Sunday. However, the Sea-Based X-band radar did not perform as expected, the agency said on its website. Officials will investigate the cause of the failure to intercept, it said. The SBX radar is a major component of the ground-based midcourse defence, the sole US bulwark against long-range missiles that could be tipped with chemical, biological or nuclear warheads. Raytheon and Boeing, which manages the overall system, had no immediate comment. Harris Corp, which provides systems engineering for the SBX radar, said their technology was not involved. It was the first time the United States had tested its long-range defense against a simulated Iranian attack. Previous drills have imitated a flight path from North Korea, another country in a standoff with the international community over its nuclear program. Speaking at the Reuters Aerospace and Defence Summit in Washington in December, Army Lieutenant General Patrick OReilly, head of the Missile Defence Agency, said the test, costing about $150 million, would break new ground. This next test ... is more of a head-on shot like you would use defending against an Iranian shot into the United States. So thats the first time that were now testing in a different scenario, he said of what turned out to be the unsuccessful test. Experts have compared the simulation to a bullet hitting another bullet in space. OReilly said the goal was to destroy the target over the north central Pacific when the missiles had a combined closing speed of more than 17,000 miles per hour. Whenever we have a situation where were taking on a missile more head on than from the side, that increases the challenges, OReilly had said. The SBX radar is mounted on a mobile, ocean-going oil-drilling platform designed to provide the layered US missile defence system with a powerful sensor that can be positioned to cover any spot on the globe.