Aug. 8 (Bloomberg) -- Democratic presidential frontrunners Hillary Clinton and Barack Obama sharpened their differences at last night's AFL-CIO forum, while they and the other candidates expressed skepticism about free trade.

New York Senator Clinton went after Illinois Senator Obama over his recent comments that he would use military force against terrorist training camps in Pakistan if the country's president, Pervez Musharraf, failed to do so. Democratic rival Christopher Dodd's criticism of those remarks last night prompted Clinton to offer some unsolicited advice to Obama.

``I don't believe people running for president should engage in hypotheticals,'' Clinton, 59, said. ``You can think big, but remember, you shouldn't always say everything you think if you are running for president, because it has consequences around the world. And we don't need that right now.''

Obama, 46, fought back by criticizing Clinton and other candidates who voted to give President George W. Bush the power to wage war against Iraq. ``I find it amusing that those who helped to authorize and engineer the biggest foreign policy disaster of our generation are now criticizing me,'' said Obama, who wasn't in the Senate when lawmakers voted to authorize the war and spoke out against it before the 2003 invasion.

The Democratic contenders are vying for support from union members, who, while dwindling in numbers, can still mobilize thousands of voters in states such as Iowa and Nevada, which hold the first two presidential caucuses in January.

Campaign Funding

Obama took on Clinton over her acceptance of campaign funds from Washington lobbyists. Obama and former North Carolina Senator John Edwards, 54, have said lobbyists have a corrupting influence on government.

``You've got to have a president in the White House who is not subject simply to the whims of corporate lobbyists,'' Obama said. ``Are we going to make certain that you have a voice in Washington, and not just those who are paying the big money in Washington to have that opportunity to negotiate?''

On trade, all but one candidate agreed that the North American Free Trade Agreement between the U.S., Canada and Mexico should be revised. Representative Dennis Kucinich of Ohio said he would scrap the 13-year-old agreement.

``Nafta is a deal that was negotiated by Washington insiders, not by anybody here tonight,'' Edwards said to cheers from the audience of 17,000 union workers.

Obama said he would ``immediately'' call the leaders of Canada and Mexico to insert labor agreements into Nafta. ``Our trade agreements should not just be good for Wall Street, it should also be good for Main Street,'' he said.

Clinton, whose husband, Bill, pushed Nafta through Congress when he was president, said the way the agreement has been implemented has hurt America.

`Smart Trade'

``I believe in smart trade, pro-American trade, trade that has labor and environmental standards, trade that's not a race to the bottom,'' the New York senator said.

Clinton, responding to criticism from Edwards and Obama that she would be beholden to corporate interests if elected president, reminded the audience that she led a failed attempt to expand health insurance in the 1990s as first lady, taking on drugmakers and insurance companies that opposed the initiative.

``For 15 years, I have stood up against the right-wing machine,'' Clinton said to applause. ``And I've come out stronger. So if you want a winner who knows how to take them on, I'm your girl.''

She said her party should unite and that she was running to ``change America,'' not ``get in fights with Democrats.''

The discussion of Obama's remarks on Pakistan, though, provoked sharp exchanges. Dodd, 63, a senator from Connecticut, called Obama's comments about Pakistan ``highly irresponsible.''

`Words Mean Something'

``Words mean something,'' said Dodd, a member of the Senate Foreign Relations Committee. ``General Musharraf is no Thomas Jefferson,'' but ``he's the only thing that stands between us and an Islamic state,'' he said.

Obama responded that it is ``common sense'' for the U.S. to militarily pursue terrorists there if necessary. ``If we have actionable intelligence on al-Qaeda operatives, including bin Laden, and President Musharraf can't act, then we should.''

At least one top union official, Harold Schaitberger, head of the International Association of Fire Fighters, thought Clinton got the better of the exchange. ``Chris Dodd and Hillary nailed Obama on that one,'' Schaitberger said.

During the debate, Obama's campaign pointed to an Aug. 1 Clinton radio interview after Obama's Pakistan speech that seemed to contradict her charges at the forum.

``If we had actionable intelligence that Osama bin Laden or other high-value targets were in Pakistan I would ensure that they were targeted and killed or captured,'' Clinton told American Urban Radio Networks, according to the Chicago Tribune.

Wider Lead

The forum came as Clinton has widened her nationwide lead over Obama to 22 percentage points, according to an Aug. 3-5 USA Today/Gallup poll.

The AFL-CIO's executive board will meet tomorrow to determine whether to move forward with the endorsement process. The labor group has said it wants to make sure that it endorses someone who can win.

Last night's forum was ``one giant job interview,'' AFL-CIO President John Sweeney said.

To contact the reporter on this story: Kim Chipman in Chicago at kchipman@bloomberg.net.

Last Updated: August 8, 2007 00:08 EDT