WASHINGTON -- White House rivals Barack Obama and John McCain on Tuesday tried to woo Hispanic voters who may prove to be crucial in the November 4 presidential election.

"I need your help. This election could well be decided by Latino voters," Democrat Obama told the League of United Latin American Citizens (LULAC), one of the country's top Hispanic organizations holding its national convention in Washington.

The Illinois Senator said he felt sure to win the White House with Hispanic voters behind him in four key states President George W. Bush won in the 2004 election.

"Every four years some of the closest contests take place in Florida, Colorado, Nevada, and New Mexico - states with large Latino communities," he told the gathering.

He urged Hispanics to register to vote in the upcoming elections.

"I truly believe that if we can register more Latinos, young and old, rich and poor, and turn them out to vote in the fall -- then not only will we change the political map, and not only will I win the presidency, but you will finally have a government that represents all Americans," Obama said.

Obama's speech followed Republican McCain's address to LULAC hours earlier, in which he stressed that border security, one of the foremost issues for US voters, would be one of his top priorities if he is elected president.

"We must prove to them that we can and will secure our borders first, while respecting the dignity and rights of citizens and legal residents of the United States," the Arizona Senator told crowd, reminding them of two failed immigration reforms in Congress he had supported in the past two years.

"But we must not make the mistake of thinking that our responsibility to meet this challenge will end with that accomplishment," he added, alluding to immigration's vital importance to the US economy, especially in farming and construction.

"We have economic and humanitarian responsibilities as well, and they require no less dedication from us in meeting them," McCain said referring to the estimated 12 million illegal immigrants living in the United States.

Obama's Democrats accuse McCain of flip-flopping and getting tougher on immigration to draw conservative Republicans to his side after they blocked the two reform bills he supported.

A recent Gallup poll put Obama ahead of McCain in Hispanic voters' intentions by 59-29 percent.

In the 2004 presidential elections, Bush garnered more than 40 percent of the Hispanic vote, a record for a Republican candidate.