A technical glitch has prompted the Pentagon's missile defense unit to scale back plans for a Friday test of a system designed to shoot down missiles heading for the U.S. mainland.

Lt. Gen. Henry A. Obering III, head of the Missile Defense Agency, said Tuesday that there were problems with telemetry cards that record data during tests of the ground-based defense missile system. Chicago-based Boeing Co. is the lead contractor on the project.

The problems, which arose from soldering of the cards, means the tests will be only a simulation of an interceptor missile striking an incoming missile. The Missile Defense Agency had planned to also run a test of the real interceptor missiles.

Obering said a similar test planned for December is expected to go ahead with a real interceptor. He would not give specifics on whether Boeing or other contractors on the project would be penalized because of the glitch. A Boeing spokesman did not immediately respond to a request for comment.

The Pentagon is building a network of sea and land-based missiles in the United States, Europe and Japan in response to longer-range missiles being developed by nations such as Iran and North Korea. Iran, which tested missiles last week, is believed to have some with a range of 1,250 miles which could reach large sections of Europe. Obering said Iran may also have an intercontinental ballistic missile capable of striking the United States by 2015.

There are now 21 ground-based interceptor missiles in Alaska and three in California. The military is currently testing them against more complicated missiles such as those where the warhead separates from the missile body in flight.