In a series of end-of-year television interviews, Martin — who had previously indicated indirectly that he supported Canadian participation in the system designed to provide a defensive shield to protect North America from missile attack — said repeatedly that Canada would not accept the weaponization of space, and would make that a condition for participation.

He set out a number of other conditions as well.

"It's going to depend on the voice we have there," he told CTV interviewers Craig Oliver and Lloyd Robertson. "We will do what is in our interest. We understand the Americans have the right to defend themselves, and they will choose that way. But from our point of view, we want to be able to protect our air space. We want to be part of the decision-making that happens there."

The U.S. missile defence system would use interceptors and land-, sea- air- and space-based sensors to meet threats of ballistic missile attack, which boosters of the program say are real, especially from nations like North Korea or Iran.

Opponents say the system, which is supposed to be partly running next year, is technically unworkable and risks destabilizing world security.

Martin said Canada is asking questions, including one about the nature of the decision-making system that will be put in place, and won't engage in the system until it has all the answers.

"We have not yet got satisfactory answers," Martin said. "If the question you're saying is `Do you want to get those answers?' the answer is yes. If you're saying to me `Will you commit?' I'll tell you we'll commit when it's in our interest to do so, and when I have the answers to those questions."

Robertson asked if it would work if Canada signed a rider saying it wouldn't go along with the weaponization of space.

"That would certainly be a very important component," Martin replied. "We will not engage in the weaponization of space. So whatever we did in this, that kind of an agreement, that kind of understanding would have to be there."

In a major foreign policy speech yesterday, Conservative Party Leader Stephen Harper attacked Martin for his indecisiveness on the subject.

"Nowhere is the current government's division and ambivalence toward the United States more evident than in its chaotic internal debate over Canadian participation in continental ballistic missile defence," he told the Canadian Club of Ottawa.

Harper said he was waiting for the smallest display of leadership and political courage from the government on the issue.

"With his party divided between those who are open to continental missile defence, those who reject it out of hand, and those who, frankly, would sign on to anything to improve their sorry record on Canada-U.S. relations, Mr. Martin gives different answers to different people on different days on his position," Harper said.

Martin spoke favourably about Canadian participation in the program in April 2003, when he was running for the Liberal leadership.

"I certainly don't want to see Canada isolated from any moves the United States might take to protect the continent," he said. "I don't see why we would walk away from the opportunity to protect the northern half, and to have a say over what happens in our airspace."

However, in the year since he has been Prime Minister, Martin has delayed making a decision on the issue, though National Defence Minister Bill Graham has argued strenuously and publicly in favour of participation.

In Martin's television interviews, conducted Monday and screened yesterday, he stressed he'd make the decision when it is in Canada's interests to do so, that Canada was opposed to the weaponization of space, and if it joined the system, would withdraw from it if it moved from a land-and-sea based system to a space-based system.

"We will not engage in the weaponization of space. Period," he told CPAC's Peter Van Dusen.