WASHINGTON (Reuters) - Presidential hopeful Joseph Lieberman warned Democrats on Monday the party's soul was at stake in 2004 and a return to the "extremes" of rivals like Howard Dean would doom it to the political wilderness.

The Connecticut senator, the most conservative of the nine Democrats vying to challenge President Bush next year, said he shared the anger of party activists over Bush's policies.

"But the answer to his outdated, extremist ideology is not to be found in outdated extremes of our own," Lieberman said in a speech on the party's future delivered at the National Press Club.

"That path will not solve the challenges of our time, and it could well send us Democrats back to the political wilderness for a long time," said Lieberman, the party's vice presidential candidate in the last election.

In the speech, Lieberman did not name the surging Dean, who appears on the cover of national weekly news magazines this week and for the first time moved slightly ahead in a poll in the crucial early caucus state of Iowa.

But aides said the remarks were aimed at the former Vermont governor, whose aggressive attacks on the war in Iraq and on the Democrats who supported it have propelled him toward the top of the pack while raising fears in the party establishment that he is leading Democrats too far left.

'TICKET TO NOWHERE'

Asked about Dean after the speech, Lieberman said a party led by a candidate who opposed the war against Iraqi President Saddam Hussein and would raise taxes was buying a "ticket to nowhere."

"In Gov. Dean's case, I respect his deeply held opposition to the war against Saddam, I just disagree with it," he said. "I think it is time to begin to speak openly, directly and with respect for one another."

A Dean campaign spokeswoman, Tricia Enright, said Dean was drawing new supporters and his campaign was ready for further attacks.

"Unlike other Democrats, we believe the only way to beat George Bush is to not be like George Bush," she said. "You've got to give people a reason to vote."

Lieberman has gone on the offensive in recent weeks to draw distinctions with the crowded field and lay claim to the party's middle ground, while his campaign slipped in some national polls and struggled to meet its fund-raising goals.

Last week, Lieberman lashed out at Dean, Sen. John Kerry of Massachusetts and Rep. Richard Gephardt of Missouri for making Democrats look weak on defense by failing to recognize the war in Iraq was justified.

On Monday he broadened the attacks, referring in general to proposals by Dean to eliminate Bush's tax cuts and the broad health care insurance plan offered by Gephardt.

"Some Democrats still prefer old, big government solutions to our problems, but with record deficits, a stalled economy and Social Security in danger, we can't afford that," Lieberman said.

"Fueled by understandable frustration, some in my party are grasping failed solutions that will not meet our 21st century needs, and will not save America from another four years of Republican misrule," Lieberman said.