"In signing this bill today, I intend to send a clear message -- that making our economy work means making sure it works for everyone, that there are no second class citizens in our workplaces," said Obama.
On average, women in the United States are paid 23 percent less than men, while minority women receive even less.
Ledbetter is an Alabama woman who discovered after 19 years on the job at Goodyear Tire & Rubber Co. that she was the lowest-paid supervisor at her plant despite having more experience than several male co-workers. A jury found she was the victim of discrimination. But during the Bush administration, the Supreme Court in a 5-4 decision reversed what critics described as decades of legal precedent by declaring that discrimination claims must be filed within 180 days of the first offense.
The court rejected the U.S. Equal Employment Opportunity Commission's contention that each new discriminatory paycheck triggers a new 180-day statute of limitations.
The law signed by Obama amended the 1964 Civil Rights Act to put the old EEOC standard into law, and covers pay discrimination based on gender, race, national origin, religion, age and disabilities.
Some Republicans and business leaders have expressed concern the measure could trigger an explosion of lawsuits based on old claims, discourage employers from hiring women and undermine efforts to stem the recession.