After weighing the highly unpopular idea for more than a year, Prime Minister Paul Martin was expected to announce a decision as soon as Thursday the report said.

Well aware that the move will cool US-Canadian relations, which had started to warm somewhat after the US-led invasion of Iraq, Martin was believed to have taken the opportunity to advise Bush beforehand at the NATO summit in Brussels, the source said.

The Liberal prime minister leads a minority government and his party's lawmakers have pressed him not to agree to take part in the program which is highly unpopular at home, particularly in Quebec.