President Bush meets Mexico's President Felipe Calderon today and will seek to reassure Mexicans he has not given up on overhauling US immigration policy.
The talks in the Yucatan, the two leaders' first summit, pose a complex challenge for Mr Bush on the final stop of a Latin American tour aimed at shoring up his standing and countering the anti-US influence of leftist Venezuelan leader Hugo Chavez.
A demonstrator takes part in a protest against US President George W. Bush's visit in Merida, Mexico
Mexico's importance to US business and trade are unrivalled in the hemisphere, but a sense of neglect has set in as Mr Bush, who promised to make Mexico a priority when he took office in 2001, has become distracted by the Iraq war.
That war has made him even more unpopular in Latin America than he is at home.
Illegal immigration from Mexico into the United States and drug trafficking are the thorniest problems between the two neighbours.
Mr Bush and Mr Calderon, a fellow conservative elected last year, are likely to find common ground after Mr Bush pledged in a visit to Guatemala yesterday to revive his push for immigration reform, saying he hopes for a breakthrough with the Democratic-led Congress by August.
"The system needs to be fixed. We don't want people to feel like they have to get stuffed into the back of a truck and pay exorbitant fees to 'coyotes' to come and try to realise dreams," Mr Bush said, referring to human smugglers who transport undocumented workers across the porous US-Mexican border.
Mexicans account for more than half of the 12 million illegal immigrants in the United States. But Mr Bush also defended recent raids leading to deportation of illegal immigrants, an approach that has drawn sharp criticism during his five-country tour of Latin America.
Mr Bush had made similar reform pledges to Mr Calderon's predecessor, Vicente Fox, who had a close rapport with the US leader but left power without an immigration deal.