Four days after calling his party affiliation a "closed issue," U.S. Sen. Joseph I. Lieberman said Sunday he was "not ruling it out" that he could turn Republican.

He told NBC's "Meet the Press" he will return to Washington as an "Independent Democrat" - "capital I, capital D."

But the R is lurking.

"I'm not ruling it out," he said, "but I hope I don't get to that point. And, I must say, and with all respect to the Republicans who supported me in Connecticut , nobody ever said, `We're doing this because we want you to switch over.'"

Lieberman also left open another controversial door - supporting more U.S. troops in Iraq .

"I think we have to be open to that as a way to succeed to achieve a free and independent Iraq , which would be an extraordinary accomplishment, but it's got to be tied to a new strategy," he said.

That strategy may be "tied to commitments from the Iraqi government to disarm those militias and to bring more Sunnis into a national unity government."

Lieberman is considered unlikely to switch to the Republican Party, but his comments triggered a fresh round of outrage by liberal bloggers Sunday. His comments came after insisting during his primary and fall campaigns that he would remain a Democrat.

He was asked about the prospect Wednesday at his post-election news conference.

"There is a little playfulness in me that wants me to make a joke about that, but it's too serious. The answer is no," he said. "When I give my word I stick with it, and I am definitely going to organize with the Senate Democrats."

Earlier last week, after delivering a speech that he called his "closing argument" for his re-election, he called the matter of his party affiliation a "closed issue."

"It is a totally closed issue. I know this is a great sport ... but I pride myself on keeping my word," Lieberman said. "And I have said explicitly that I will, if I am re-elected, I will organize with the Democrats."

Democrats know they have to be careful not to offend Lieberman. They will hold a fragile 51 to 49 majority in the Senate next year. A switch by Lieberman would swing the majority to the GOP, because Vice President Dick Cheney would break tie votes.

Republicans have said they have no intention of trying to get Lieberman into their caucus. Asked about the prospect Thursday, outgoing Republican Party Chairman Ken Mehlman said no high-level effort is being made.

"We take him at his word, that he's staying a Democrat," Mehlman said.

Lieberman won re-election last week by garnering about 70 percent of the Republican vote and 33 percent of Democrats, according to exit polls.

Some national observers have called him potentially the most powerful person in the Senate, because he is beholden to no party. But Lieberman also knows that if he wants to become chairman of the Senate Homeland Security and Governmental Affairs Committee, he needs to stay a loyal Democrat.

He reiterated that point Sunday.

"I'm going to caucus with the Democrats ... because it's good for my constituents in Connecticut ," he said.

But he also stressed his independence, saying he was following the model of former Sen. Harry F. Byrd Jr. of Virginia . Byrd, a Democrat, became an independent in 1970 after refusing to sign a pledge to back all Democratic nominees.

Byrd won re-election as an independent in 1976, but became an ally of Republicans on most matters.

Asked on "Meet the Press" whether he would switch to the GOP, Lieberman said, "Well, that's a hypothetical, which I'm not going to deal with. I'm going to be an optimist and take some encouragement from the fact this was an election in which, in the House and Senate, Democrats came to the majority of both chambers by electing moderates mostly."

He noted that the election found "voters in Connecticut and elsewhere saying we're disappointed with the Republicans. We want to give the Democrats a chance."

At the same time, he said, "I believe that the American people are considering both major political parties to be in a kind of probation, because they're understandably angry that Washington is dominated too much by partisan political games and not enough by problem-solving and patriotism, which means put the country and your state first. "