The agency has been trying to conduct the test, which would be the first of its kind in two years, since the middle of last week, but has had to put it off three times due to weather conditions.

"The missile defense test scheduled for this evening has been postponed due to continuing bad weather at Kwajalein Atoll," said Rick Lehner of the Missile Defense Agency.

"A decision will be made on Sunday afternoon to conduct the test Sunday night, contingent on weather conditions at Kwajaelin Atoll and Kodiak, Alaska," he said.

An interceptor missile is to be fired from Kwajalein Atoll in the Marshall Islands into the path of a target missile launched from Kodiak Island, Alaska.

Although this test could result in an intercept, the Missile Defense Agency says the aim is to gather data in preparation for a full fledged intercept attempt next March or April.

In earlier tests, target missiles have been successfully intercepted in five out of eight attempts. But since the last test in December 2002, flight tests have been delayed or cancelled six times, adding to questions about the viability of the system.

Despite the lack of recent flight tests, President George W. Bush is expected to declare the system operational by the end of this year.

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