The US military failed to shoot down a ballistic missile in a test resembling an Iranian or North Korean strike after a radar malfunctioned, a spokesman said on Monday.

The test was carried out on Sunday at a US Army site at the Kwajalein Atoll in the Marshall Islands but the target missile was not intercepted as planned, said Rick Lehner, spokesman for the Missile Defense Agency.

The ground-based interceptor was launched from Vandenberg Air Force base in California and performed "normally," but the the sea-based X-band radar "did not perform as expected" in the test, the MDA said in a statement.

Officials had launched an investigation into the test and it would take "several weeks before they have an initial report," Lehner told AFP.

The target missile in the test represents "the type of technology that a country such as North Korea or Iran might be able to develop in the future that would threaten the United States," he said.

The test came as the Pentagon released a report that warned Iran and North Korea continue to pursue long-range ballistic missiles and described both countries' intermediate and shorter-range missiles as "regional threats" to US forces, allies and partners.

The Ballistic Missile Defense Review Report also voiced concern over Syria's mobile, short-range missile arsenal that can reach much of Israel, parts of Iraq, Jordan and Turkey.

Sunday's test follows reports that the US military was speeding up deployment of defenses against potential Iranian missile attacks in the Gulf to heed off any possible retaliation.

The move involved moving ships off the Iranian coast and anti-missile systems in at least four Arab countries -- Qatar, the United Arab Emirates, Bahrain and Kuwait -- the New York Times reported, citing administration and military officials.