WASHINGTON — The run-up to Stephen Harper's first face-to-face meeting with George W. Bush took on a cordial tone Monday as both leaders thanked one another for the recent rescue of three hostages in Iraq, including two Canadians.

In a 20-minute phone call initiated by Harper, the two men discussed their meeting this week in Mexico, chatted about softwood lumber and touched on the rescue of the hostages after four months in captivity in Baghdad, said White House spokesman Frederick Jones.

Both men expressed gratitude for the roles each of their countries played in the freeing of the hostages. The Conservative government has not provided details on the extent of the Canadian involvement in the rescue.

"They thanked each other,'' a Harper spokesman said late Monday. "At the beginning of the conversation, both acknowledged the contribution American, British, Canadian and Iraqi forces made to ensuring (the hostages) were successfully freed and returned home.'' Harper and Bush also spoke briefly about the prime minister's recent trip to Afghanistan, during which Harper made it clear Canada has no intention of pulling out troops stationed there, said the Prime Minister's Office, which also described the phone call as "private.''

The friendly tone is expected to continue when the men meet on Thursday in Cancun.

Lots of smiles, extended handshakes for the cameras, and warm expressions of friendship will be on the agenda, sources say.

But those are just the public displays of affection.

Behind the scenes, the Conservative government is changing the very structure of its departments to reflect a new focus on Canada-U.S. relations.

Earlier this month, staff at Foreign Affairs and at International Trade were told their departments would be reunited. Former prime minister Paul Martin had split them in two, creating an administrative nightmare that was still sorting itself out when the Liberals were defeated in January.

Now they'll be back together again, and the Conservatives have approved a major expansion of the mega-department's North American branch.

Anything that touches on trade or politics between Canada and the United States or Mexico will be in a centralized office _ sources say a more strategic approach than in previous years. Affairs with all other countries will be dealt with under another branch.

The reorganization reflects the prime minister's determination to make the relationship with the United States a priority.

Martin came to office promising a "more sophisticated'' approach to Canada-U.S. relations. He left after the engaging in a nasty public spat with American ambassador David Wilkins.

Harper's meeting with Bush is part of trilateral meeting with Mexico's Vicente Fox. The three are expected to focus largely on the Security and Prosperity Partnership, an accord that deals both with protecting North America from outside attacks but also with ensuring competitiveness in global markets.

But that's hardly the part of the trip that the Conservative government is fixated on.

Harper and Bush will have a one-on-one meeting together on Thursday for the first time since the Conservatives were elected. If there's a moment for a thaw of Canada-US relations, this will be it.

"It will set the right tone and set a sense of direction that will allow for productive results throughout the prime minister's mandate,'' said a senior Foreign Affairs official.

Harper is expected to raise a number of issues with Bush, including the stalemate over softwood lumber and concerns over Washington's plan to require passports or other secure documents at every point of entry to the United States.