WASHINGTON -- Mexican President Vicente Fox, the first state visitor of the Bush presidency, challenged the United States on Wednesday to strike an agreement on immigration by year's end. President Bush said "there is no more important relationship" than with Mexico but did not embrace Fox's ambitious deadline.

The public challenge stunned U.S. officials who have been trying to lower expectations for a deal on the complex and politically risky issue that could legalize millions of undocumented Mexicans. Even some Mexican officials said they had no notice that Fox would push for quick action.

The two-day state visit, an important political event to both Bush and Fox, began promptly at 8:30 a.m. when a military band struck up a Sousa march and the two presidents strolled shoulder to shoulder onto the White House back lawn. Military honor guards stood stone-faced as their battle ribbons, jostled atop flag poles by a cool wind, whipped at their faces.

Bush, hoping to court Hispanic voters for his 2004 re-election bid, said Wednesday's formal welcoming ceremony, one-on-one Oval Office session, rare joint Cabinet meeting and state dinner -- along with his and Fox's joint trip today to Ohio -- amounted to a "recognition that the United States has no more important relationship in the world."

With all the pageantry a president can muster, Bush welcomed Fox to what he called the "Casa Blanca" and said, "We understand that our two nations must work together in a spirit of respect and common purpose to seize opportunities and tackle challenges on the issues that affect the lives of our citizens, including migration, the environment, drugs, crime, corruption and education."

Dominating issue

That included just a glancing reference to the issue that dominates U.S.-Mexican relations: What should be done with the 3 million or so illegal Mexican immigrants who want legal status in America, and millions more in Mexico who want to cross the 2,000-mile border? The president wants an undetermined number of illegal immigrants to become legal.

A joint statement being released today as Bush and Fox tour a Hispanic community center in Toledo, Ohio, commits the pair to forging a "realistic approach to migration" that respects "the human dignity of all migrants, regardless of their status."

With a dozen anti-immigration protesters outside the White House gates, Bush and first lady Laura Bush threw Fox an intimate state dinner with an extraordinary finale of fireworks on the South Lawn.

Raising a glass of 7-Up, the teetotaling Bush toasted Fox "friend to friend, partner to partner, neighbor to neighbor." Fox returned the compliment, calling Bush "Jorge" and someone he trusts to take action on the immigration problem.

Bush's trip to Mexico in February raised hopes in both countries that an agreement would come quickly, but the leaders have sounded more cautious in recent weeks as congressional conservatives raised objections.

On the eve of their meetings, Bush said the complexity of the issue bars a quick deal and acknowledged that he has "a lot more selling to do" in Congress. Fox said Sunday it would take four to six years to complete a comprehensive U.S.-Mexican immigration overhaul.

Flanked by Bush in front of the Truman Balcony, Fox seemed to set a more aggressive timetable.

"We must and we can reach an agreement on migration before the end of this very year which will allow us, before the end of our respective terms, to make sure that there are no Mexicans who have not entered this country legally in the United States and that those Mexicans who have come into the country do so with the proper documents," said Fox. His term ends in 2006.

Call for agreement

Fox appeared to be calling for an agreement that would be ready for consideration by the respective legislatures of the two countries before the end of the year. But U.S. officials have said that details such as timetables and the numbers of Mexicans who would be eligible have not yet been broached.

Fox believes Mexicans in the United States are not being treated fairly. He says U.S laws should be amended so that migrants receive health, education and labor rights and can work without fear of deportation.

Several administration officials said afterward they would have preferred to avoid the added pressure of a public deadline. The officials, speaking on condition of anonymity, said it is impossible to predict whether a comprehensive agreement can be reached this year, given the unease in Congress and fluidity of the talks.

Bush, asked whether he thought Fox's timetable was too ambitious, pretended not to understand the question and joked in Spanish, "I can't hear."