Changes to U.S. President Barack Obama's historic health-care reform bill have been approved by Congress.

The Democrat-controlled House voted 220-207 Thursday evening on legislation that modified the bill Obama signed two days earlier. The approved changes include improved benefits for seniors, for low-income and middle-class households.

In the early hours of Thursday, Republicans managed to stall the law by finding flaws in minor provisions to the bill. The provisions dealt with federal Pell Grant student aid program for low-income students.

The provisions were stricken out and a vote on the amended bill was held Thursday afternoon on the changes in the Senate. The move passed 56 to 43, with Republicans unanimously opposed along with three Democrats. Vice President Joe Biden presided over the ballot in case his vote was needed to break a tie.

The law was later approved by the House. Both chambers must approve identical legislation before it can be sent to the White House. The measure will now be sent to U.S. President Barack Obama's desk for his signature.

Thursday's surprise developments came after Senate Democrats managed to kill 30 other Republican amendments to the bill Wednesday.

Democrats methodically rejected each of them in turn during a none-hour sessions, including amendments to proposals to deny erectile dysfunction drugs to sex offenders, and to prevent tax increases for families earning less than $250,000.

Senate Democratic leader Harry Reid complained that the attempted revisions were not meant to improve this bill.

"There is an attempt to destroy this bill," Reid said as voting on the amendments stretched to nine hours. "Not a single one has been adopted. I don't know what they are trying to accomplish here."

Senate Minority Leader Mitch McConnell rejected that accusation, saying: "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."

The first version of the US$940 billion overhaul narrowly passed on Sunday by a vote of 219-212, after a bitter year-long political struggle.

The landmark legislation will see 32 million Americans gain health care coverage and ban insurance companies from denying coverage to patients with pre-existing conditions, among other measures.

Under the new system, most Americans will have to buy health insurance, whether through their employer, the government or through a private company. If they fail to do so, they will face a fine from Washington -- a contentious point among dissenters who say the bill foists unwanted government involvement in their health care.

No Republicans voted for the overhaul, which will change how almost every American receives and pays for medical treatment. Many in the party are predicting it will prove devastating in November for the Democrats who voted for it.

With reports from Associated Press