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CLEVELAND, Feb 26 (Reuters) - Democrats Barack Obama and Hillary Clinton clashed sharply in a high-stakes one-on-one debate on Tuesday, accusing each other of falsely portraying their stances on health care, trade and other issues.

Clinton, who needs to win next week in Ohio and Texas to keep her U.S. presidential campaign alive after Obama's streak of 11 straight victories, went on the attack early in the debate at Cleveland State University in Ohio.

Obama fired back repeatedly in several testy but controlled exchanges during a debate that seemed unlikely to change the dynamic of the race before next Tuesday's contests.

The debate was sharper in tone than last week's encounter in Texas, but far less personal and angry than a Democratic debate last month in South Carolina.

Clinton kept up her recent criticism of Obama campaign literature sent to Ohio voters that she said mischaracterized her health care proposal, which includes mandates requiring Americans to purchase health insurance.

"We should have a good debate that uses accurate information, not false, misleading and discredited information, especially on something as important as whether or not we will achieve quality, affordable health care for everyone," the New York senator said.

Obama, an Illinois senator, said Clinton has frequently misrepresented his health care plan, which does not include mandates and which some critics suggest could leave 15 million Americans uninsured.

An estimated 47 million Americans -- about a sixth of the population -- now have no health insurance, either privately or through the government.

Clinton, once the odds-on favorite to win the Democratic nomination to contest November's presidential election against the Republican candidate, has lost big leads in public opinion polls in Ohio and Texas as Obama has gained momentum and made inroads among her supporters.

Obama said he was interested in bringing the cost of health care down and enforcing mandates could create a burden on some low-income Americans. Clinton's criticisms, he said, were part of a consistent pattern.

"Senator Clinton has ... constantly sent out negative attacks on us, e-mail, robo-calls, flyers, television ads, radio calls, and we haven't whined about it because I understand that's the nature of these campaigns," he said.

"But to suggest somehow that our mailing is somehow different from the kinds of approaches that Senator Clinton has taken throughout this campaign I think is simply not accurate."

AGGRESSIVE CLINTON

With her campaign on the line, Clinton has aggressively challenged Obama in the last few days, questioning his readiness to become commander in chief and chiding him for the health care campaign literature sent to Ohio voters.

In the debate, she attacked Obama for claiming she supported the North American Free Trade Agreement, which she said she believes should be renegotiated. She was first lady when her husband, President Bill Clinton, approved the deal.

The trade agreement is unpopular in Ohio, where it has been blamed for contributing to a broad loss of manufacturing jobs in the state.

"You know, I have been a critic of NAFTA from the very beginning. I didn't have a public position on it because I was part of the administration. But when I started running for the Senate, I have been a critic," Clinton said.

Obama repeated the charge and said he would push to have NAFTA redone.

"I think that it is inaccurate for Senator Clinton to say that she's always opposed NAFTA. In her campaign for Senate, she said that NAFTA, on balance, had been good for New York and good for America," he said.

Clinton complained about having to take the first question more often than Obama, and made reference to her campaign's charges that he gets an easier ride from the national media than she does.

She pointed to a television skit that portrayed a fawning press posing questions to Obama.

"If anybody saw 'Saturday Night Live,' you know, maybe we should ask Barack if he's comfortable and needs another pillow," she said. "I just find it kind of curious that I keep getting the first question on all of these issues."

Clinton, who has questioned Obama's foreign policy experience, also stumbled over the likely new Russian president when asked if she knew the name of the successor to President Vladimir Putin -- Dmitry Medvedev.

"Medvedev -- whatever," she finally said.

The two contenders revisited their differences on the Iraq war. Clinton said Obama, an early opponent of the war, had the advantage of not being in the Senate in 2002 when she voted to authorize the war.

But Obama said her vote "facilitated and enabled" President George W. Bush's decision to go to war.

"Senator Clinton often says that she is ready on day one, but in fact she was ready to give into George Bush on this critical issue," Obama said. (Editing by Lori Santos and John O'Callaghan) (To read more about the U.S. political campaign, visit Reuters "Tales from the Trail: 2008" online at

blogs.reuters.com/trail08/