WASHINGTON -- Senate Republicans on Tuesday blocked a bill that would have ensured women are paid the same amount as their male counterparts.

The Senate failed to secure the 60 votes needed to advance the Paycheck Fairness Act, which would have required employers to demonstrate that any salary differences between men and women doing the same work are not gender-related. The bill also would have prohibited employers from retaliating against employees who share salary information with their co-workers, and would have required the Labor Department to increase its outreach to employers to help eliminate pay disparities.

The final vote was 52-47, with all Republicans opposing the bill. That included female Sens. Kelly Ayotte (N.H.), Susan Collins (Maine), Kay Bailey Hutchison (Texas), Lisa Murkowski (Alaska) and Olympia Snowe (Maine).

President Barack Obama called it "incredibly disappointing" that Republicans would block a bill relating to equal pay for women.

"This afternoon, Senate Republicans refused to allow an up-or-down vote on the Paycheck Fairness Act, a commonsense piece of legislation that would strengthen the Equal Pay Act and give women more tools to fight pay discrimination," Obama said in a statement. "It is incredibly disappointing that in this make-or-break moment for the middle class, Senate Republicans put partisan politics ahead of American women and their families."

After the vote, Senate Majority Leader Harry Reid (D-Nev.) used a procedural maneuver that gives him the ability to bring up the bill again on another day. He said he would leave the door open to taking it up again in another form.

"It is a very sad day here in the U.S. Senate," Sen. Barbara Mikulski (D-Md.), the author of the bill, said after the vote. "But it's a sadder day every day when a paycheck comes and women continue to make less than men. We are sorry that this vote occurred strictly on party lines."

Mikulski said she refuses to let her bill "die on parliamentary entanglements" and, after quoting Abigail Adams, called on women everywhere to keep fighting until the bill becomes law.

"Put on your lipstick! Square your shoulders! Suit up and let's fight for a new American revolution where women are paid for equal work!" Mikulski shouted. "Let's end wage discrimination in this century once and for all."

Republicans opposed the bill for different reasons. Sen. Scott Brown (R-Mass.) signaled Monday night that he wouldn't support it because he thinks it may burden small businesses. Sen. Marco Rubio (R-Fla.) told reporters Tuesday that he didn't think the bill would do the job and said it "reads more to me like some sort of welfare plan for trial lawyers."

Collins told reporters that "we already have on the books the Equal Pay Act, the Civil Rights Act and the Lilly Ledbetter Act, which I did support. I believe that they provide adequate protections. I think this bill would result in excessive litigation that would impose a real burden, particularly on small businesses. So I think existing laws are adequate."

"In other cases, it may be due to personal decisions that women make to leave the workforce to raise children for a number of years and then return to the workforce, for example," Collins continued. "I don't think you can assume discrimination."

Regardless of their belief in the bill's policies, Democrats are also clearly pushing the bill for political reasons. Obama jumped on a press call Monday to personally throw his support behind the bill. House and Senate Democrats have slammed Mitt Romney for staying silent on the issue, and White House officials have teamed up with Democrats for calls and press conferences to call attention to the fact that Republicans won't support the measure.

Mikulski demurred when asked during a Monday press call why, if the issue is so pressing, Democrats didn't push the bill when they held the majority in the last Congress. She said Democrats chose to move first on a related bill, the Lilly Ledbetter Act, and lost their majority in the Senate before they could bring up the Paycheck Fairness Act.

White House senior adviser Valerie Jarrett, who was also on the Monday press call, said that Obama has no plans to issue an executive order to implement the bill, in the event it can't pass Congress.

"There is no interest right now in talking about a fallback," Jarrett said. "We are confident that if we focus on working hard, we can pass it. We want to keep focused on the best alternative."

Michael McAuliff contributed to this report.