Republicans at a House-Senate conference on Thursday pushed through an agreement on legislation that would save employers some $80 billion in pension payments over the next two years.

Democrats, saying their efforts at compromise had been rebuffed, promised to defeat it in the Senate.

House and Senate negotiators broke along party lines in approving the pensions relief bill (search), which for the next two years would change the formula by which single employer pension plans pay into their funds.

The bill, actively sought by business groups, could allow thousands of companies to divert money now paid into pension plans into investment and new hiring.

But the bill ran into trouble when the White House, and Republicans in the House, resisted language in the Senate version of the bill that would also provide two years of relief to multiemployer plans (search), generally run jointly by unions and management in such trades as construction and trucking.

The House is expected to approve the bill on Friday, the last day before it leaves on a two-week recess.

The Senate will be in session next week, and Democratic senators said the bill would be defeated because of the multiemployer dispute.

The White House, said Sen. Edward Kennedy, D-Mass., "played an ideological card, a punitive card. That has to be rejected."

Sen. Charles Grassley, R-Iowa., chairman of the Senate Finance Committee, lamented the failure to find common ground. "I think that with just a little bit of give it could have been very bipartisan," he said.

The White House has threatened a presidential veto (search) if the bill contained any relief for multiemployer plans, saying such plans are not experiencing the same financial crisis as single-employer plans and that the relief would encourage underfunding of plans. Democrats say the White House stance is indicative of an anti-union bias.

The House side on Thursday put forth an offer, apparently acceptable to the White House, that would restrict help to only the neediest 4 percent of multiemployer plans. Grassley proposed changes that would raise the number of eligible plans to about 10 percent, but that was rejected by the House negotiators.

House Education and the Workforce Chairman John Boehner, R-Ohio, said that his side believed "we've gone as far as we can go on the multiemployer section and still get a bill signed into law."

He said failure to reach an agreement would "put in jeopardy millions of American workers."

Single-employer plans must make quarterly payments in their pension plans by April 15, and without congressional action they will be forced to determine those payments on a now-outdated interest rate formula that would inflate what they owe.

A Senate vote against the conference report would send the bill back for more negotiations. Sen. Max Baucus, D-Mont., top Democrat on the Finance Committee, said he had received calls from airline companies that morning "scared to death" that Congress would fail to pass a bill.

The legislation also has provisions that help financially struggling airlines and steel companies with underfunded plans cut back on what they are required to pay into "catch-up" funds.

The two-year limit on the bill is aimed at giving Congress time to work on long-term reforms to the pension system.