Washington, March 24 (IANS) Minutes after President Barack Obama signed sweeping health care reform legislation into law, 14 opposition Republican states went to court as the party vowed to do everything to undo the historic measure.

Obama hailed the legislation as the latest example of America facing up to major challenges for the benefit of all its people as he used 22 pens to ceremonially sign the controversial law providing for the biggest expansion of federal health care guarantees in more than four decades.

Obama and Democratic leaders celebrated the new law at the White House signing ceremony, with a crowd packing the East Room repeatedly standing to applaud and cheer the president.

"It's been easy at times to doubt our ability to do such a big thing, such a complicated thing, to wonder if there are limits to what we as a people can still achieve," Obama said.

"We are not a nation that scales back its aspirations," he said. "We are not a nation that falls prey to doubt or mistrust. We don't fall prey to fear."

No Republicans supported the bill in either the House or Senate and Democratic leaders needed a separate "fixes" bill to get reluctant House Democrats to approve the Senate's version of the health care reform bill.

Hours later, the Senate launched debate on the "fixes" with Republicans promising to use every parliamentary tool available to undermine or defeat the measure.

Meanwhile, 14 states mounted a legal challenge arguing that the legislation's requirement that individuals buy health insurance violates the Constitution. A lawsuit filed by 13 states in a federal court in Pensacola, Florida, called the act an "unprecedented encroachment on the sovereignty of the states" and asks a judge to block its enforcement.

The case was filed by Florida Attorney General Bill McCollum and joined by his counterparts in South Carolina, Nebraska, Texas, Utah, Louisiana, Alabama, Michigan, Pennsylvania, Colorado, Idaho, South Dakota and Washington.

Virginia's attorney general, Ken Cuccinelli, filed a separate case in his state Tuesday afternoon. Louisiana's Attorney General Buddy Caldwell is a Democrat, but the State's Indian-American governor Bobby Jindal is a Republican.

But McCollum said the case is "not a partisan issue," and predicted other Democrats would join the suit.

At least one of the officials who signed onto the lawsuit has run into criticism back home. Washington Governor Chris Gregoire, a Democrat, criticised Republican Attorney General Rob McKenna for joining the case and said she would actively oppose the suit.