May 22 (Bloomberg) -- Senator Joe Lieberman, a Connecticut independent, says his disagreement with the Democrats over the Iraq war won't prevent him from working with his former party. For now.

``I hope the moment doesn't come that I feel so separated from the caucus'' that he decides to shift allegiance to the Republicans, he said in an interview. Asked what Democratic actions might cause such a break, he invoked Supreme Court Justice Potter Stewart's famous 1964 definition of pornography: ``I'll know it when I see it.''

The 65-year-old lawmaker is the margin of difference in the Democrats' 51-49 control of the Senate. A switch to the Republicans, which he won't rule out, would create a 50-50 tie that would allow Vice President Dick Cheney to cast a deciding vote for Republican control.

Lieberman has ``gone from being dispensable to essential for the Democrats,'' said Ross Baker, a political scientist at Rutgers University in New Brunswick, New Jersey.

Lieberman said he already has seen much he doesn't like from the Democrats, particularly Majority Leader Harry Reid's decision to co-sponsor, and then allow a vote last week on, legislation cutting off war funding by March.

`A Fundamental Disagreement'

Leiberman said Reid's recent remark that the war is lost undermined troop morale and left him ``terribly'' bothered. ``I just have a fundamental disagreement,'' he said.

The senator, the Democrats' 2000 vice presidential nominee, was defeated in last year's primary after three terms by anti- war candidate Ned Lamont. Lieberman created a new line on the ballot, ``Connecticut for Lieberman,'' and won a five-way general election with 50 percent of the vote.

Democratic leaders wooed him to caucus with the party this year, naming him chairman of the Homeland Security and Governmental Affairs Committee. At one point, Lieberman stopped attending weekly party caucus meetings, though he resumed at Reid's behest.

Lieberman said that while he has experienced ``moments of real awkwardness and aloneness,'' he generally relishes his added clout and ability to stake out independent positions: ``The first words that come to mind are that I've returned feeling empowered and liberated.''

Using His Leverage

He has already used his leverage to help Republicans thwart efforts by Reid earlier this year to pass a resolution expressing opposition to President George W. Bush's plan to send 21,500 additional U.S. troops into Iraq. He has voted against his former party on every bill and every amendment demanding troop withdrawals this year.

Still, Reid, 67, heaps praise on Lieberman. ``As strongly as he is opposed to what the vast majority of Democrats want, he also has been a gentleman within the caucus,'' the Nevadan told reporters May 3. ``We don't have a greater gentleman in the Senate than Joe Lieberman.''

Other Democrats say the knowledge that they need Lieberman's support to keep their majority is a source of tension. ``I think it's fair to say that the differences on the war carry a bit of angst,'' said Senator Frank Lautenberg of New Jersey.

At times, Lieberman appears more pro-war than even many Republicans. Some House members warned Bush this month that the war is hurting the party and they are prepared to defect; party leaders in both chambers said this month that lawmakers will re- evaluate matters in September. That's when General David Petraeus, the top U.S. commander in Iraq, tells Congress whether the recent increase in troop levels is helping stabilize the country.

`We Can Still Succeed'

Lieberman, meanwhile, said it may take a lot more to change his mind on the war, which he says is vital to U.S. national security. ``I believe very strongly that we can still succeed in Iraq,'' he said. ``Unless Petraeus comes back and says it's hopeless, I'm going to stick with the program.''

The senator said his new-found independence may extend to presidential politics. In the interview, he said he is intrigued by talk of an independent candidate in the 2008 race. He also often praises Arizona Senator John McCain, a Republican contender and fellow war-supporter. He has had much less to say about his fellow Connecticut senator, Chris Dodd, who supported Lamont in last year's race and is now running for president.

``It's quite possible I would support a Republican or independent,'' Lieberman said.

Middle Ground

In the meantime, he's staking out what he says is the middle ground in the Senate. With Senator Lamar Alexander, a Tennessee Republican, he established a monthly gathering for senators of both parties to help break down partisan tension and draft bipartisan bills.

His top legislative goals this session include measures increasing the number of visas for highly skilled immigrants and curbing domestic oil consumption by encouraging production of alternative fuels and more fuel-efficient cars. Both have support among Republicans and Democrats.

In his home state, Lieberman is less popular than he used to be. A May 2-7 Quinnipiac University poll found he had a 53 percent approval rating among registered Connecticut voters. His record approval rating, 80 percent, came in September 2000, when he was campaigning as Al Gore's vice presidential running mate.

Still, Lieberman said, his rating is strong enough: ``It's two points higher than I got in the election,'' he laughed.

To contact the reporter on this story: Laura Litvan in Washington at llitvan@bloomberg.net

Last Updated: May 22, 2007 00:12 EDT