The follow-up health care bill being considered by the Senate will have to return to the House for final congressional approval, after the Senate parliamentarian determined that two Republican challenges will succeed in stripping out language in the package. 

Altering the bill in any way means it has to return to the House side, which first approved the package of changes Sunday, since both chambers must pass identical versions. 

Democrats don't appear worried. Jim Manley, spokesman for Senate Majority Leader Harry Reid, said the House could easily approve the expected changes. The Senate is expected to complete work on the bill Thursday afternoon, and the House could take it up again the same day -- or push it off until Friday. 

The package of changes, which is being considered under "reconciliation" rules allowing the Senate to approve it with just 51 votes, is the final piece of the legislative puzzle to the health care reform package signed into law Tuesday. Health care reform is officially enacted, but House Democrats wanted the package of fixes to change the way it's financed and address other concerns. 

The glitches have to do with Pell grants for low-income students. 

A senior Senate Republican leadership aide told Fox News that Democrats had tried to improve the cost of the bill while simultaneously piling on Pell grants "without mandating the spending." The aide said Democrats claimed the grants would increase, but were relying on a "future Congress" to find the funding. 

"They can't do that," the aide said. "This was one of 100 gimmicks used to keep the score down." 

Republicans have been hunting for such violations in hopes of bringing down the legislation. Democrats had also been consulting with the parliamentarian, Alan Frumin, and hoped they had written a measure that would not be vulnerable to such problems. 

The two provisions are expected to be formally removed from the bill on Thursday. Both chambers are hoping to begin a spring recess by this weekend. 

The president, who signed the landmark legislation into law on Tuesday, was flying to Iowa later in the day for the first of many appearances he will make around the country before the fall congressional elections to sell his health care revamp. 

Obama was appearing in Iowa City, where as a presidential candidate in 2007 he touted his ideas for health coverage for all. His trip comes with polls showing people are divided over the new health law, and Democratic lawmakers from competitive districts hoping he can convince more voters by November that it was the right move. 

Besides reshaping parts of the landmark health overhaul, the legislation transforms the federal student loan program -- in which private banks distribute the money -- into one in which the government issues the loans directly. That produces some federal savings, which the bill uses in part to increase Pell grants to needy students. 

The latest development came as the Senate completed nine hours of uninterrupted voting on 29 GOP amendments to the legislation. Majority Democrats defeated every amendment. 

The legislation would change the new health care law by making drug benefits for Medicare recipients more generous by gradually closing a gap in coverage, increasing tax subsidies to help low-income people afford health care, and boosting federal Medicaid payments to states. 

It kills part of the new statute uniquely giving Nebraska extra Medicaid funds -- designed to lure support from that state's Sen. Ben Nelson -- that had become a glaring embarrassment to Democrats. It also eases a new tax on expensive health coverage bitterly opposed by unions and many House Democrats, while delaying and increasing a new levy on drug makers. 

As they began pushing the bill to passage on Wednesday afternoon, Democrats ran into a mountain of GOP amendments. Outnumbered and all but assured of defeat, Republicans forced votes on amendments aimed at reshaping the measure -- or at least forcing Democrats to take votes that could be used against them in TV ads in the fall campaigns. 

"There's no attempt to improve the bill. There's an attempt to destroy this bill," said an exasperated Reid, D-Nev. 

"The majority leader may not think we're serious about changing the bill, but we'd like to change the bill, and with a little help from our friends on the other side we could improve the bill significantly," answered Senate Minority Leader Mitch McConnell, R-Ky. 

By 57-42, Democrats rejected an amendment by Sen. Tom Coburn, R-Okla., barring federal purchases of Viagra and other erectile dysfunction drugs for sex offenders. Coburn said it would save millions, while Sen. Max Baucus, D-Mont., called it "a crass political stunt." 

Democrats also deflected GOP amendments rolling back the health law's Medicare cuts; killing extra Medicaid funds for Tennessee and other state-specific spending; barring tax increases for families earning under $250,000; and requiring the president and other administration officials to purchase health care from exchanges the statute creates. 

The landmark legislation that Obama signed Tuesday would provide health care to 32 million uninsured people, and make coverage more affordable to millions of others by expanding the reach of Medicaid and creating new subsidies. Insurance companies would be forbidden to refuse coverage to people with pre-existing illnesses, individuals could buy policies on newly created exchanges and parents could keep children on their family plans until their 26th birthdays. 

The $938 billion, 10-year price tag would be financed largely by culling savings from Medicare and imposing new taxes on higher income people and the insurance, pharmaceutical and medical device industries. 

The Associated Press contributed to this report.