DANVILLE, Ky. -- Republican Dick Cheney and Democrat Joseph Lieberman disagreed firmly but politely Thursday night about military readiness, tax cuts and the future of Social Security in a gentlemanly debate of campaign understudies.

Sitting a few feet apart around a small table, the vice presidential candidates agreed that President Slobodan Milosevic should give up power in Yugoslavia after an election loss, but both opposed the use of American troops to force him out.

In a debate that ranged broadly over campaign issues, Lieberman, a two-term Connecticut senator, said Republicans want to "raid the Medicare trust fund to pay for their tax cuts." But Cheney said there was more than enough money to go around, and it is "totally reasonable" to give relief to all taxpayers.

The argument that "somehow ... all of it is going to tax cuts isn't true," Cheney said of the huge surpluses forecast over the next decade.

The two men sparred as they sat together for their only debate of the fall campaign. The atmosphere on a specially constructed stage at Centre College was far more relaxed than Tuesday night when presidential candidates Al Gore and George W. Bush met in Boston for the first of their three scheduled encounters.

Each man pledged at the outset to avoid personal attacks. Cheney took that one step further. "I promise not to bring up your singing," he said to Lieberman.

"And I promise not to sing," Lieberman replied with a smile.

But even good-natured comments reflected the widely differing views the two men hold about the role of government in the 21st century.

Pointing to a strong economy, Lieberman said most people would say they are better off then they were eight years ago. "I am pleased to see from the newspapers that you're better off than you were 8 years ago too," he said to Cheney, a reference to the multi-million dollar separation package the former oil services company executive received when he left to join the GOP ticket.

"And I can tell you, Joe, that the government had nothing to do with it," Cheney said -- a remark that overlooked that his firm had received more than $2 billion in federal contracts for support of American troops on peacekeeping missions.

Lieberman joked that his wife wanted him to join the private sector.

"Well, I'm going to try to help you do that, Joe," Cheney said.

"No, I think you've done so well there I want to keep you there."

The two men debated in a White House race that is as close as any in the past four decades. Bush and Gore are separated by only a point or two in most polls, pointing to a suspenseful final month of the campaign.

When the subject turned to legalized gay marriage, the rivals responded gingerly. Lieberman said "my mind is open" though he wants to preserve the institution of heterosexual marriage.

Cheney, who has an openly gay daughter, said people should be open-minded and tolerant of gays but the issue of gay marriage is "not a slam dunk." He said it was appropriate for states to regulate marriage. "I think different states are likely to come to different conclusions."

Asked by moderator Bernard Shaw about a public uprising in Yugoslavia designed to force out Milosevic, Lieberman and Cheney both said they hoped he would surrender power, but ruled out the use of American troops. Lieberman said a U.S.-led bombing campaign last year had halted Milosevic's aggression.

Cheney hearkened back to Tuesday night's debate. "There appears to be under way an effort to get the Russians involved," the former defense secretary said. "Governor Bush suggested exactly that ... and Al Gore pooh-poohed it," he added. "But now it's been reported in the press that in fact that is exactly what we're doing, that Governor Bush was correct in his assessment and his recommendation."

Cheney added the situation was an opportunity to test President Vladimir Putin of Russia. "We ought to find out whether he is indeed committed to democracy, whether he is committed to support the forces of freedom and democracy."

On another foreign policy issue, Cheney said the United States "might have no other choice" but military action to oust Iraqi leader Saddam Hussein if he is found to be developing weapons of mass destruction. Cheney was defense secretary during the Persian Gulf War, which Lieberman noted "did not end in total victory."

The running mates reviewed well-worn campaign disagreements over Social Security.

Lieberman said he and Gore have a proposal that would guarantee benefits to current recipients through at least 2054. He conceded that he had recently investigated suggestions that individuals be allowed to invest some of their own funds. "Sometimes you have to dig deep to find out if there's oil in the well. I drilled into that, and the deeper I got, the drier the well became," he said.

Bush has called for allowing younger workers to take control over investment of 2 percent of their own Social Security payroll taxes, a step he says would increase their total investment returns. Cheney said Gore's proposal contained no overall reform to safeguard the future of the retirement program.

When it came to defense readiness, Cheney said there has been an erosion during the eight years of the Clinton administration, and the Pentagon was "overcommitted and under-resourced."

"With all due respect, this administration has a bad track record," he said, citing reports that some units were only permitted to conduct live firing exercises twice a year.

Lieberman replied that the United States was "ready to meet any commitment that might arise," and scolded Cheney for his comments in the midst of a political campaign.

A question about whether Lieberman had flip-flopped on his positions since joining Gore's ticket produced a carefully worded reply from Cheney. Cheney said he felt "the depth of concern" that Lieberman once showed had lessened about entertainment material that wasn't fit for children. "You haven't been as consistent as you have been in the past," he said.

Lieberman said he disagreed, but readily apologized for a joke told by a comedian at a recent fund-raiser that was critical of Bush's religion.