President Bush told Canadian Prime Minister Paul Martin on Saturday he understood his decision to opt out of the planned US missile defense system, in a conciliatory gesture ahead of Mr Martin's visit to the United States.
In a phone call initiated by Mr Martin, Mr Bush raised the subject of missile defense and the two leaders discussed it briefly, according to US and Canadian officials.
"The president expressed his understanding of the prime minister's decision, but underscored the importance of redoubling our security cooperation efforts," White House spokeswoman Erin Healy said.
An aide to Mr Martin described Mr Bush as "conciliatory and very positive."
"The president said both sides need to move on," said the Canadian aide, who added that Mr Bush praised Canada's plan to bolster its defense budget over the next five years.
Canada's minority Liberal government announced on Feb. 24 that it would not take part in the missile defense system, which is designed to shoot down ballistic missiles from adversaries such as North Korea.
The program has been marred by test failures and it failed to meet the president's goal of being operational by the end of last year.
Mr Martin, who came to power in 2003 saying he supported signing on to the missile shield and deepening the integration of the two countries' defenses, had been under heavy pressure to back away from the system because of its lack of popularity with Canadian voters.
The tone of Bush's comments during the call marked a change from the initial US reaction, in which Secretary of State Ms Condoleezza Rice expressed disappointment and put off plans to visit Canada.
Mr Martin will join Mr Bush and Mexican President Vicente Fox at the U.S. president's Crawford, Texas, ranch on March 23. Mr Bush is to hold sessions with the two leaders at nearby Baylor University before hosting them for lunch at his "Prairie Chapel" ranch.
In addition to missile defense, Mr Bush and Mr Martin talked of taking a common approach to persuade Japan and South Korea to open their markets to North American beef after the mad cow scare.
Lending support to Canada in its push to reopen US borders to Canadian beef, Mr Bush earlier this week pledged to veto a bill approved by the Senate that would block imports of Canadian cattle.