CANCUN, Mexico (AP) – President Bush, closing a three-nation summit Friday, defended requiring secure documents from border-crossing Canadians and pushed Mexico to prevent more of its people from illegally entering America

Despite obvious divisions, Bush, Mexican President Vicente Fox and Canadian Prime Minister Stephen Harper emphasized North American unity and the productivity of their two days of meetings in this sunny spring-break area along Mexico’s Mayan Riviera.

From a luxury hotel’s indoor tennis court, gussied up with carpet, custom podiums and large video screens, the men emerged from joint sessions to laud the increased trade brought about by the 12-year-old tariff-reducing North American Free Trade Agreement.

The leaders said they intend to build on that progress – Canada and Mexico are the U.S.’s largest trading partners – to make their continent more competitive globally. And they pledged cooperation on new energy sources and bird-flu preparations.

“This is probably one of the most productive meetings we’ve had,” Bush gushed to Fox, the meeting host and a friend dating to before both assumed their nations’ presidencies. Fox said, “We have made a very good use of time.” And Harper announced a third annual trilateral meeting for next year in Canada – again framed around the Security and Prosperity Partnership the three nations formed a year ago.

But, with disagreements still lingering – over everything from a Mexican murder investigation that has ensnared two Canadian mothers to a U.S.-Canada trade conflict over lumber and Mexico’s long-unrealized hope for a migration accord with the United States – there was little concrete to show for the leaders’ enthusiasm.

The long-standing dispute over U.S. tariffs on Canadian softwood lumber that is a major irritant in Ottawa didn’t even come up Friday, perhaps a sign of how stalemated the issue is. The day before, Bush had promised only to “negotiate in good faith and a timely fashion” while Harper threatened legal action if agreement is not forthcoming.

The requirement that all people coming into the United States after 2007 – whether from Canada or Mexico – present a passport or some other tamper-proof document is another subject of great concern that Harper raised. Bush said he understands the fears, but didn’t back down.

“Congress passed a law and I intend to enforce the law,” the president said. “I believe this can be done in such a way that it makes future travel, future relations stronger, not weaker.”

From Cancun, Bush flew to Texas for a weekend at his ranch.

Bush and Fox have reunited on the immigration issue after years of strained relations over Mexico’s opposition to the Iraq invasion and because of the back-burner status of a migration accord.

But the alliance is tempered by Mexico’s disappointment that broader legalization for Mexicans in the United States is not in the immediate offing, by repeated U.S. demands that Mexico crack down on its own border, and by a sometimes-angry debate now raging in Washington that leaves it anything but certain whether immigration overhaul will happen.

With congressional elections set for the fall, Bush’s Republican Party is split over the issue. The Senate is debating a bill that would legalize many illegal immigrants in the United States and expand “guest-worker” programs for an estimated 400,000 immigrants each year, in addition to enhancing border security. With many conservatives opposed to guest worker programs, the House has passed rival legislation that focuses only on getting tough on illegal immigration.

Siding with business leaders looking for a steady supply of workers, Bush reiterated his demand that the GOP-controlled Congress approve a guest-worker program that would allow illegal immigrants to work legally, though temporarily, in the United States.

“I said I want a comprehensive bill,” he said. “I believe there will be a comprehensive bill.”

Bush gently chided those who have been talking about the issue – and his position on it – in unusually heated terms. Believing a guest-worker program would spur illegal immigration, hurt national security, abandon American middle-class workers and provoke a backlash from voters, House conservatives lobbed harsh criticism at the president in a Thursday news conference.

“I expect the debate to bring dignity to America, in recognition that America is a land of immigrants and people ought to be treated with respect,” Bush shot back.

In a nod to his party’s priorities, though, Bush also emphasized the need for Mexico to enforce its side of the border, and praised Fox for recent seriousness on the subject. “It’s very important to enforce laws,” he said.

Fox said he’s committed to border security, but he also said the sticky issue between Mexico and its northern neighbor can only be solved “under the framework of a legislation that will guarantee legal, orderly, safe and respectful migration.”