WASHINGTON — An alternative economic stimulus package picked up momentum in the Senate on Wednesday with new Republican support, potentially complicating the bid to pass legislation quickly to pump billions of dollars into the ailing economy.

The Senate economic package, which would offer lower rebates than the House version but send them to many more Americans, won a 14-7 bipartisan nod in the Finance Committee.

The proposal could come up for debate in the Senate as soon as today as an alternative to a House plan that passed with overwhelming Republican support Tuesday.

Three Republicans joined 11 Democrats in supporting the Senate measure after Sen. Charles Grassley, R-Iowa, the ranking member, endorsed it.

The Senate plan, drafted by Finance Committee Chairman Max Baucus, D-Mont., would offer rebate checks to nearly all but the wealthiest taxpayers and would pump approximately $193 billion into the economy over the next two years. It would cost the Treasury $152 billion over the next decade, according to the Joint Committee on Taxation.

Its centerpiece is a proposal to send $500 rebate checks to individuals, including senior citizens and many upper middle-class taxpayers who were excluded in the House legislation. Couples would get $1,000, with an additional $300 for each child. People with incomes of more than $150,000 or couples with incomes of more than $300,000 would be ineligible for the rebates.

The measure would also extend unemployment benefits by 13 weeks. Baucus’ plan also includes temporary tax breaks for businesses.

Under the House plan, approved 385-35, single filers would get a $600 rebate that would begin phasing out for taxpayers earning more than $75,000. Married couples would get $1,200 and $300 for each child. That rebate would start to phase out at $150,000.

The House bill also includes business tax breaks and a large one-year increase in the size of mortgages that can be backed by the government, making it easier for homeowners to refinance into more-affordable mortgages. It would inject an estimated $161 billion into the economy over the next two years and cost the Treasury $117 billion over the next decade, according to the Joint Committee on Taxation.

Baucus’ decision to offer his own economic-stimulus legislation has drawn criticism from House leaders, as well as the president and his GOP allies in the Senate. They have urged swift approval of the House bill, a compromise worked out between the White House and House leaders. Several Republican senators repeated that plea Wednesday and voted against the Baucus measure in committee.

But, like the House measure, the Senate plan might be altered.

Senators in recent days have proposed a host of additions, including billions of dollars for public works projects, home heating assistance and housing aid. On Wednesday, the Finance Committee added a tax package to promote renewable energy and a tax refund for the coal industry for export taxes found to be illegal.

If the Senate approves its own economic-stimulus package, it would have to be reconciled with the House version before it is sent to the president, which could delay its enactment.

Senate Majority Leader Harry Reid, D-Nev., has said he wanted to complete work on the package by Feb. 15. Rebate checks would not begin arriving until May.