The president picked the Lilly Ledbetter Fair Pay Act for the first piece of legislation to sign as president.

He appeared before a packed East Room audience for a ceremony, and Ledbetter stood at his side.

His entrance in the room was met with hearty cheers from the many labor and women's groups represented there. House Speaker Nancy Pelosi, the first woman speaker in the history of Congress, and Secretary of State Hillary Clinton, were present. Clinton went further than any woman previously in her campaign for the presidency, although she ultimately lost the Democratic Party competition to Obama.

The measure is designed to make it easier for workers to sue for decades-old discrimination. He said "this is a wonderful day."

The law effectively nullifies a 2007 Supreme Court decision that said workers had only 180 days to file a pay-discrimination lawsuit.

Ledbetter said she didn't become aware of a pay discrepancy until she neared the end of her 19-year career at a Goodyear Tire & Rubber Co. plant in Gadsden, Ala. She sued, but the Supreme Court in 2007 said she missed her chance.

The court said in its 5-4 ruling that a person must file a claim of discrimination within 180 days of a company's initial decision to pay a worker less than it pays another worker doing the same job. Under the new bill, given final passage in Congress this week, every new discriminatory paycheck would extend the statute of limitations for another 180 days.

Congress attempted to update the law to extend the time, but the Bush White House and Senate Republicans blocked the legislation in the last session of Congress

Opponents contended the legislation would gut the statute of limitations, encourage lawsuits and be a boon to trial lawyers. They also argued that employees could wait to file claims in hopes of reaping larger damage awards. The bill does not change current law limiting back pay for claimants to two years.