U.S. Senate on Thursday voted to block an effort to repeal the ban on gays and lesbians to serve openly in the military, upholding the ban for now.

The Senate voted 57-40 in the vote, which fell short of the 60 votes needed to overcome procedural hurdles. The repeal of the Clinton-era "Don't ask, don't tell" policy is running out of time to pass the Democratic controlled Senate this year. The chamber can try again before the Congress breaks for holidays next week. Come next year, it may become more difficult to pass as more Republicans who oppose the repeal will join the Senate.

The "Don't ask, don't tell" policy, which was introduced as a compromise measure in 1993 by then-President Bill Clinton, prohibits homosexuals to serve openly in the military. It has been a major contentious issue in U.S. politics. Critics including gay rights groups argue that the policy violates the rights of gay military members to free speech and open association.

The issue has come under increasing scrutiny as a lawsuit challenging the 17-year-old law worked its way through the federal courts this year, and is scheduled to be heard by a federal appeals court in the spring. President Barack Obama, Secretary of Defense Robert Gates and Chairman of the Joint Chiefs of Staff Mike Mullen have said they support congressional repeal of the law.