Barack Obama said here Thursday that his "biggest failure" as president has been the lack of progress on immigration reform and expressed regret for having been "naive" to think Republicans would work with him on the issue.

The Democratic incumbent offered that admission toward the end of a "Meet the Candidate" forum organized by Univision, the nation's leading Spanish-language network.

Univision anchors Jorge Ramos and Maria Elena Salinas posed questions in Spanish and Obama answered in English before a Democratic audience at the University of Miami.

"(W)hat I'm absolutely certain of is if the Latino community and the American community that cares about this issue turns out to vote, they can send a message that this is not something to use as a political football, that people's lives are at stake, that this is a problem that we can solve and historically has had bipartisan support," the president said when Ramos asked about the chances of immigration reform if Republicans retain control of the House of Representatives.

"So my hope is, is that after the election ... if they (the Republicans) have seen that people who care about this issue have turned out in strong numbers, that they will rethink it, if not because it's the right thing to do, at least because it's in their political interest to do so," Obama said.

After starting the conversation with a question about current events in the Middle East, Ramos confronted the president over his failure to keep his 2008 campaign promise to pass immigration reform.

"You promised that. And a promise is a promise. And with all due respect, you didn't keep that promise," Ramos said to Obama.

The president said his first months in office were dominated by efforts to deal with an economy "on the verge of collapse."

"But even in that first year," he insisted, "one of my first acts was to invite every single member of Congress who had previously been supportive of comprehensive immigration reform, and to say to them, we need to get this done."

"There's the thinking that the president is somebody who is all-powerful and can get everything done," Obama said.

"In our branch, in our system of government, I am the head of the executive branch. I'm not the head of the legislature, I'm not the head of the judiciary," he said.

"And what I confess I did not expect - and so I'm happy to take responsibility for being naive here - is that Republicans who had previously supported comprehensive immigration reform - my opponent in 2008 (Sen. John McCain), who had been a champion of it and who attended these meetings - suddenly would walk away. That's what I did not anticipate," Obama said.

"What I promised was that I would work every single day as hard as I can to make sure that everybody in this country, regardless of who they are, what they look like, where they come from, that they would have a fair shot at the American Dream. And I have - that promise I've kept," he said.

The president added that while he has never "wavered" in backing immigration reform, Republican rival Mitt Romney has said "he would veto the DREAM Act, that he is uncertain about what his plan for immigration reform would be, and who considers the Arizona law a model for the nation and has suggested that the main solution for immigration is self-deportation."

Romney, appearing in a separate "Meet the Candidate" forum at UM on Wednesday night, rejected mass deportation but was otherwise non-committal on his approach to the immigration issue.

Obama took more than 60 percent of the Latino vote in 2008 and polls show him with a similar lead over Romney among Hispanics. EFE