WASHINGTON — Democratic presidential candidate John Kerry called Wednesday for deeper tax cuts for the middle class than proposed by President Bush and described his Republican critics as "the most crooked . . . lying group I've ever seen." The chairman of Bush's re-election campaign called on Kerry to apologize "for this negative attack."

After urging labor leaders to support his campaign, Kerry met with one-time rival Howard Dean to discuss an endorsement and what role the former Vermont governor might play in his campaign.

Hoping to win over Dean, the presumptive nominee's staff greeted the fallen rival with a round of applause as he walked into Kerry headquarters. The two men shook hands, embraced briefly and raised joined hands for the cameras.

After the 45-minute meeting, officials close to the talks said Dean will endorse Kerry, with only the timing in question. The officials, speaking on condition of anonymity, said the best time might be March 25 when the presidential candidates join former Presidents Bill Clinton and Jimmy Carter for a Democratic Party fund-raiser.

"I will work closely with John Kerry to make sure we beat George Bush in November and turn our country around," Dean said in a statement that did not specifically mention an endorsement.

"There is a lot we can do together to rebuild an America that belongs to all of us, and we'll be saying more about what our amazing grass-roots network can do to help with his goal." Dean has set March 18 to announce details of his grass-roots advocacy organization.

Kerry was scheduled to meet with another key rival, John Edwards, on Thursday.

Anticipating their meeting, the Bush campaign issued "Howard Dean's Greatest Hits on John Kerry," a 10-item recounting of Dean's criticisms. The quotes from news stories include Dean's statement in January that "you're not going to change America by nominating somebody who's a Washington insider whose biggest long suit is talk."

Kerry had 2,037 delegates after sweeping four Southern primaries Tuesday, an Associated Press analysis showed. He wasn't expected to reach 2,162, the number needed to secure the nomination, until next week.

Earlier Wednesday in Chicago, Kerry toughened his comments about his GOP critics after a supporter urged him to take on Bush. "Let me tell you, we've just begun to fight," Kerry said. "We're going to keep pounding. These guys are the most crooked, you know, lying group I've ever seen. It's scary."

Bush-Cheney campaign chairman Marc Racicot called on Kerry to apologize.

"Senator Kerry's statement today in Illinois was unbecoming of a candidate for the presidency of the United States of America, and tonight we call on Senator Kerry to apologize to the American people for this negative attack," Racicot said in a statement.

"On the day that Senator Kerry emerged as his party's presumptive nominee, the president called to congratulate him. That goodwill gesture has been met by attacks and false statements."

Kerry spokesman David Wade said earlier that Kerry was referring to Republican critics in general and that the comment was intended to convey the message that "he's a Democrat who fights back."

The Bush-Cheney campaign didn't see it that way. "John Kerry has run a relentlessly negative campaign from the very beginning and this comment is completely consistent with that," the campaign said.

In a satellite address to top AFL-CIO leaders meeting in Florida, Kerry said a "Bush Tax" stemming from the president's economic policies has driven up costs for working families. He vowed to reverse that trend while asking those making more than $200,000 a year to pay the same taxes they paid under Clinton, effectively repealing portions of a tax cut Bush pushed through Congress.

Kerry also proposed creating a $50 billion fund to help states provide relief from state and local taxes for working families that he said have been struggling.

"Under George Bush's policies, middle-class families are paying more," he said. "America's middle class can't afford a tax increase. That's why we're going to give the middle class a tax cut."

In response, the Bush campaign accused Kerry of favoring broad tax increases that would affect all taxpayers.

"John Kerry has voted for higher taxes 350 times and his numbers for new spending don't add up," said Steve Schmidt, a Bush campaign spokesman. "His campaign-trail promises mean he is going to raise taxes by at least $900 billion." It is the first time the Bush campaign has put a number on tax hikes it says Kerry favors.

Kerry said a middle-class tax cut would do far more to spark the economy than what Bush has pushed, by helping people afford college costs, pay for health care and make ends meet.

"If this president wants to make this election about taxes after he's cut billions for billionaires and given middle-class families a larger share to pay, we're ready for that fight," he said.

Kerry also addressed Democratic National Committee staff, seeking to end speculation that chairman Terry McAuliffe's role will be diminished. "No one can do what this man has done," Kerry said, according to Kerry and DNC aides in the private meeting.

Contributing: Ron Fournier.