In mid-August, the missile interceptor was again set to go when technicians found a glitch in the booster's flight computer. Replacing the computer created another delay.
In September, program officials announced yet another postponement after discovering modifications that had been made to the interceptor without thorough ground testing.
With everything in place again Dec. 8, the test was put off five more times in the past week as a result of bad weather, first in Alaska and then in the Marshall Islands, followed by problems with a range radar in the Pacific and with a battery in the target missile, according to Rick Lehner, spokesman for the Missile Defense Agency.
"There's obvious disappointment," Lehner said when asked about the reaction at the agency. "We'll identify the anomaly and fix it. But I wouldn't want to speculate on how that might affect operation of the system. I guess that will depend on what the anomaly turns out to be."
Lehner also said it is too early to predict when the next flight might be attempted. The Pentagon had planned to conduct an intercept test in the spring.
In addition to the six interceptors in place in Alaska at Fort Greely, a second launch site at Vandenberg Air Force Base in California received its first interceptor last week and is due to get another later this month. Next year, 10 more are scheduled to be installed at Fort Greely and two more at Vandenberg.
In Canada, meanwhile, Prime Minister Paul Martin said in television interviews Tuesday night that his country will participate in a U.S. missile defense system only if it does not have to contribute money, no missiles are based in Canada, and Canada has a say in how the system is run.
Martin was pressured two weeks ago by President Bush to end his government's wavering and commit to supporting the system.
Martin spelled out a strong Canadian position. He said he would insist that the United States guarantee in writing that no weapons will be put in space.
The National Post, a Toronto newspaper, predicted that Martin's demands would be seen by the U.S. administration as "arrogant and unrealistic." Public opinion polls in Canada have shown that joining the missile defense system is highly unpopular.
Correspondent Doug Struck in Toronto contributed to this report.