US President Barack Obama and Republican nominee Mitt Romney on Wednesday night fought head-to-head here over economy, the top issue on the campaign trail, among several domestic issues in their first face-to-face debate.

The somewhat subdued incumbent and the generally more aggressive challenger began their first prime-time debate side-by-side at Denver University in Denver, Colorado.

The 90-minute debate, hosted by veteran PBS journalist Jim Lehrer, started off with a question to Obama on how he would create jobs, and went on concentrating on the important issue of economy for half of the time.

Obama opened his statement on economy by stressing the debate was not about "where we have been" but rather where the nation was heading to.

Romney aggressively questioned Obama's economic record and accused his economic policies as a "trickle-down government" burdening the US economy.

"I am concerned that we are on the path that's just been unsuccessful. The president has a view very similar to the one he had when he ran for office four years ago, that spending more, taxing more, regulating more -- if you will, trickle-down government -- would work. That's not the right answer for America, " said Romney.

Obama rebutted by saying Romney's economic plans lacked details. "I think the American people have to ask themselves, is the reason that Governor Romney is keeping all these plans to replace secret because they are too good?" said Obama.

The two candidates also tried to sharpen their contrast with each other over domestic issues including healthcare, government regulation and the role of government.

On health care, Obama related the Affordable Care Act, his signature domestic achievement, to the similar idea of what Romney had institutionalized in Massachusetts as the state governor and now opposed as a presidential candidate.

Romney defended himself that his plan differed from having the federal government take over health care across America. He said Obama's health care overhaul raised cost of healthcare and cut Medicare, and the president used his precious first term to push forward the plan instead of creating more jobs.

Romney also attacked Dodd-Frank Wall Street Reform and Consumer Protection Act, signed into law by Obama in 2010, saying it had helped create too-big-to-fail Wall Street banks, while crushing small community banks.

Obama, on the other hand, defended his record, questioning Romney's "repeal and replace" approach. He stressed Wall Street needs reform and supervision, while families needs protection in the healthcare insurance market.

As they moved on to the topic of the role of government, Obama stressed the federal government role of opening up opportunity and create ladders of opportunity.

"There is also something we do better together," said Obama.

Romney said the role of the government is to protect the principals of the Constitution and the Declaration of Independence, but not to substitute government to people's initiatives.

Obama was heading into the debate with a clear advantage in polls. The latest poll by Pew Research Center found that more voters, by a margin of 51 percent to 29 percent, said Obama would do better than Romney in the first debate.

But the debate had higher stakes for Romney, as he was trailing the president in polls.

Prior to the debate, both campaigns had said it would give the candidates an opportunity to speak directly to voters without the filter of the media.

The two camps clearly had different evaluation of the candidates' performance during the first debate.

It was now becoming "painfully apparent" for the sitting president that when it came to the issues of economy, jobs, the taxes, the budget, "he has no clue," said Republican Senator Marco Rubio in remarks to media on spot after the debate.

David Plouffe, the long-time Democratic strategist and the campaign manager for Obama's 2008 campaign, said the president intensified in the first debate over cases the campaign had been making through the campaign trial, including Romney's tax cut plan, Medicare as well as the Wall Street reform and Romney had to defend most of the time on those issues.

The debate was the first of three debates Obama and Romney would participate in this election, and their running mates are going to debate each other once.

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The two US presidential candidates on Wednesday fought hand-to-hand over economic topics including job creation and the government deficit during their first presidential debate held in Denver, Colorado.

President Barack Obama, from the Democratic Party, who is seeking his reelection, said the United States has been back to economic growth and job creation, as the nation's private sector has created about 5 million job opportunities in the past 30 months.

US presidential debate draws strong reaction

Local reaction to the first presidential debate in Colorado history was strongly positive, as supporters of both President Barack Obama and Republican challenger Mitt Romney claimed victory for their candidates.

An estimated 50 million Americans watched the debate on TV, in which Romney rejected the claim that he will cut taxes for the richest and called for the creation of new jobs and reduction of national debt.