Canadian Prime Minister Paul Martin called US President George W. Bush on Saturday and the two leaders exchanged views on Canada's decision to opt out of a US-led anti-ballistic missile shield program, the White House said.

"The president expressed understanding of Martin's decision but underscored the importance of redoubling our security cooperation efforts,'' White House spokeswoman Erin Healy said.

Martin announced late last month that Canada would not participate in the missile defense program, saying he would not support the "weaponization of space."

Washington has expressed disappointment with Martin's decision.

US Secretary of State Condoleezza Rice reportedly canceled her trip to Ottawa scheduled for mid-April.

During their 15-minute conversation, Healy said, Bush and Martin also "expressed the importance of our ongoing cooperation in NORAD (the North American Aerospace Defense Command) to continental security."

Bush is due to meet Martin and Mexican President Vicente Fox on bilateral and regional issues on March 23 at Baylor University in Waco, Texas, and host a lunch for them at his ranch in nearby Crawford, the White House said on Tuesday.

Source: Xinhua