Merida, Mexico ? President Bush pledged Wednesday to intensify his push for languishing immigration legislation, standing alongside Mexican President Felipe Calderon who acknowledged he has relatives picking vegetables in the U.S.

Calderon said the family members pay taxes in the United States and “probably handle that which you eat, the lettuce, etc.” But he avoided saying whether they were there legally.

The joint news conference with Calderon was Bush’s last appearance in a weeklong Latin America tour that included stops in Brazil, Uruguay, Colombia and Guatemala. The trip was designed to emphasize U.S. aid for the region and counter criticism that the United States has neglected Latin America.

The president was generally warmly received throughout his travels, and streets were packed with curious onlookers. Still, there were protests at nearly every stop, and Bush was shadowed from afar by Venezuela’s fiery leftist president, Hugo Chavez, who conducted his own tour of Latin America and taunted the president nearly daily.

U.S. immigration laws were a prime topic for Bush. The president said his most important ally in getting Congress to overhaul immigration rules may be a longtime nemesis of Republicans, Sen. Edward M. Kennedy, D-Mass. Once Republicans put aside differences and settle on a course, Bush said, Kennedy may be the one to lead the charge in the now-Democratic Congress because of his vast legislative experience.

“My mood is optimistic because the mood in Congress seems like it’s changed,” Bush said.

Calderon has complained U.S. immigration laws are too harsh and has criticized U.S. plans to add up to 700 miles of new fencing along the border. He said he supports efforts by Bush to ease the law. Bush wants to establish a guest-worker program and a path to citizenship for many of the estimated 12 million undocumented immigrants in the United States.