As Congress returned to work yesterday, President Clinton urged GOP lawmakers to join with him to adopt health reforms pent up on Capitol Hill, including tougher regulations of HMOs, safeguards to keep patients' medical records private and steps to expand Medicare and keep it from going broke.

"There are a lot of pessimists who think that nothing's going to happen here this fall, that the parties are just going to fight and maneuver and get ready for next year," the president said. "I think they're wrong."

But as Clinton was talking bipartisanship, the mood in Congress was less conciliatory. With the president unyielding in his opposition to the Republicans' centerpiece $792 billion tax cut, Senate Majority Leader Trent Lott (R-Miss.) and other Republicans warned there would be little ground for compromise if the president vetoes their tax plan.

"It's obvious he doesn't want a fair tax relief package, it's obvious he wants to spend more money, and it's obvious he wants to . . . spend Social Security money for other programs," Lott told reporters, casting doubt on prospects for a tax agreement with the president. "He hasn't made any sounds or given any signals that he has a desire to do that."

As they head into a critical period of decision-making this fall, Congress and the White House are at odds over tax and spending policy, as well as other issues such as Social Security, Medicare, health care, gun control and campaign finance.

At the White House, Clinton reminded an audience of health care advocates--and, more important, the lawmakers newly returned from a month-long recess--of eight changes to the health care system that the administration has been prodding Congress to adopt.

While his views are not new, the president's tone yesterday was a marked contrast to the jabs he has thrown recently at congressional Republicans, whom he has accused of obstructing the administration's agenda.

"Health care cannot be a partisan issue," Clinton said. He exhorted Congress's GOP leaders to schedule votes quickly on the legislation, which he said is widely supported by the public and by members of both political parties.

Clinton devoted the greatest attention yesterday to a "patients' bill of rights" the administration has been touting for nearly two years, which would give more clout to Americans in health maintenance organizations and other managed care plans.

This summer, the Senate approved a narrower set of protections that would help about one-third of the Americans with private health insurance, and Clinton immediately vowed to veto it.

The issue's fate in the House remains uncertain. A month ago, the administration threw its support behind a bipartisan patients' rights bill that appears to have enough GOP supporters to pass but is opposed by the House leadership. An alternative is scheduled to be introduced today by two Republicans, Reps. Tom Coburn (Okla.) and John Shadegg (Ariz.). Speaker J. Dennis Hastert (R-Ill.) initially signaled that he favored their approach, but he now appears to have reservations.

Clinton also renewed his call for Congress to help patients on Medicare pay for prescription drugs and to devote $300 billion from expected budget surpluses over the next decade to help prevent the health insurance program for the elderly from running out of money. The Senate Finance Committee has promised to draft a Medicare reform bill by this fall, but it remains unclear when it will be ready.

On Capitol Hill, the major topic of the day was tax and spending, with Republicans complaining about the president's unwillingness to back their tax plan, and Democrats warning that GOP budget plans would wreak havoc in housing, space and other domestic programs.

Lott emerged from a Senate GOP policy lunch complaining that while Republicans have demonstrated a willingness to compromise, the White House has yet to reciprocate. "He's not joined us on tax relief, he's not joined us on Medicare, he keeps sending us more [requests] for appropriations bills for Washington government," he said.

Lott said that if Clinton vetoes the tax bill next week, when Republicans plan to send it to him, he would oppose trying to negotiate a smaller, compromise package. Instead, he said, Congress and the White House should kick over the tax issue to the 2000 election year, and focus instead on completing work on the must-pass appropriations bills.

But Lott's view isn't universally shared among GOP leaders, and Hastert refused to rule out another attempt at agreement on a tax cut if Clinton makes good on his veto threat. "We need to see what the president is going to do with this," Hastert said.

A combative Senate Minority Leader Thomas A. Daschle (D-S.D.) told reporters, "There is virtually no support throughout the country for a tax cut today."

And other Democrats questioned the GOP spending priorities. Housing and Urban Development Secretary Andrew M. Cuomo joined House Democrats yesterday in blasting Republicans for promoting a major tax cut while cutting $2 billion from the president's housing budget request. "We are generating more revenue than ever and the response of the Republicans to the working poor is, 'Tough, you get cuts,' " said Rep. Barney Frank (D-Mass.).

Staff writer Helen Dewar contributed to this report.