Congressional bargainers criss-crossed the Capitol all day yesterday and into the night, shuttling between negotiating sessions in an effort to iron out the final details of a deficit-reduction package that has eluded Congress and the Bush administration for months.

None of the major unresolved items -- details of the tax increases, Medicare savings, proposed Medicaid expansion and changes in the budget process -- was expected to waylay the tentative accord as it winds its way through the legislative labyrinth in what lawmakers hope are the final hours of the 101st Congress.

"With the White House optimistic, one would guess it would be hard to shipwreck the thing," said Rep. Bill Frenzel (Minn.), the ranking Republican on the House Budget Committee.

Last night, it appeared unlikely that the plan would be ready for House consideration by this afternoon, as congressional leaders had hoped. "We're doing everything we can to get this thing through," said Senate Finance Committee Chairman Lloyd Bentsen (D-Tex.).

Bentsen met one-on-one with House Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.) last night to settle the remaining differences in the tax component of a plan intended to save $500 billion over five years, including $40.1 billion in the fiscal year that began Oct. 1. Even though most other congressional leaders had given their approval to the most crucial elements, the two powerful chairmen were still haggling over the fine points.

Other lawmakers strived yesterday to wrap up the rest of Congress's work and get home to campaign for the congressional elections, now just 12 days away. "My great hope . . . is that we can finish on Saturday night," House Majority Leader Richard A. Gephardt (D-Mo.) said to his colleagues' applause yesterday.

But if the House does not vote on the deficit-reduction plan today, that hope could be dashed. If the session extends to Sunday, lawmakers could find themselves in the midst of a scheduled Capitol Hill rally by the Ku Klux Klan.

Although many details of the deficit-reduction package remained unresolved last night, the final product is likely to even out the top two marginal tax rates at 31 percent. That would be an increase from 28 percent for the approximately 600,000 highest-income Americans and a cut from 33 percent for 3.5 million upper-middle-income taxpayers.

But the measure also would limit the benefit of the tax deductions claimed by higher-income taxpayers and gradually eliminate their $2,050 personal exemption. People who earn between $51,300 and $125,000 would pay more Medicare payroll taxes. Higher federal taxes would hit those who drive, smoke, travel on commercial airlines, drink alcoholic beverages and buy such expensive items as furs, jewelry, luxury automobiles, boats and private airplanes.

The final deal is expected to include an expansion of the earned-income tax credit, which benefits the working poor.

Overall, the package would net as much as $160 billion in new tax revenue over the next five years, more than $20 billion more than the failed budget-summit agreement envisioned, according to administration officials.

Disputes lingered last night over provisions that would lose rather than raise tax revenue. Bentsen, for instance, was pressing a $2.5 billion, five-year package of tax breaks for oil and gas exploration. The Senate bargainers were seeking about $5.6 billion over five years for a variety in tax breaks for small businesses. Rostenkowski was resisting the inclusion of any tax breaks in the measure.

On Medicare, Senate bargainers accepted the House-passed savings level of about $42 billion over five years, but differences remained over how to achieve those savings. Only about $10 billion would result from higher costs to beneficiaries. The amount of out-of-pocket costs they must pay before receiving benefits for the voluntary coverage of physicans and outpatient hospital services would rise from $75 to $100. Monthly premiums for the same program, currently $28.60, would gradually rise to $46.20 by 1995.

The remaining savings would come from lower payments to physicians and hospitals, and negotiators were still discussing hospital reimbursement formulas.

On Medicaid, Democrats were pressing a proposal, opposed by the Bush administration, that would expand benefits for the elderly poor by about $2.9 billion over five years. The administration had agreed to extra Medicaid spending during the summit talks to assist senior citizens who might have trouble meeting Medicare premium increases. Although the size of the premium increases have been greatly reduced, Democrats do not want to give up the extra money.

As bargaining continued, Republicans said they were worried about the chances of last-minute trouble. "What you thought you had, you aren't really sure until they really zip it up," said House Minority Leader Robert H. Michel (R-Ill.).

White House Chief of Staff John H. Sununu, Treasury Secretary Nicholas F. Brady, and Office of Management and Budget Director Richard G. Darman urged House Republicans not to delay final passage of the package. Any delay, they argued, would prevent President Bush from campaigning against Democrats and for GOP candidates.

House GOP leadership aides predicted that only between 50 or 60 House Republicans would vote for the package. That would require the support of between 160 and 170 of the House's 258 Democrats to pass the measure. House Democrats are expected to provide that support, despite elements in the package that trouble many of them.

Meanwhile, OMB has begun work on the fiscal 1992 budget, due on Capitol Hill in about three months. Staff writer Tom Kenworthy contributed to this report.