WASHINGTON -- The Senate is moving forward on the first major bill barring workplace discrimination against gays in nearly two decades as Americans' shifting views about homosexuality have significantly changed the political dynamic.

Seven Republicans and 54 Democrats stood together Monday and cleared the bill past its first hurdle on a 61-30 procedural vote in the 100-member chamber, setting the stage for debate on Tuesday and possible passage by week's end. The Employment Non-Discrimination Act would prohibit workplace discrimination against gay, bisexual and transgender Americans.

The legislation, the first significant gay rights bill since Congress ended the ban on gays serving openly in the military in 2010, faces strong opposition in the House, with its Republican leader, Speaker John Boehner, rejecting the measure.

Final passage would cap a 17-year quest to secure Senate support for a similar discrimination measure that failed by one vote in 1996, the same year Congress passed and President Bill Clinton signed the Defence of Marriage Act, the law prohibiting federal recognition of same-sex marriage.

Americans have displayed a greater acceptance of homosexuality while Republicans, who struggled to win over young people and independents in the 2012 presidential election, have searched for supporters beyond their core base of older voters. The Supreme Court in June affirmed gay marriage and granted federal benefits to legally married same-sex couples while same-sex marriage is legal in 14 states and the Washington federal district.

A Pew Research survey in June found that more Americans said homosexuality should be accepted rather than discouraged by society by a margin of 60 per cent to 31 per cent. Opinions were more evenly divided 10 years ago.

About a half hour after the Senate acted, President Barack Obama cited the vote as an example of "common sense starting to prevail" in a Congress that has opposed much of his agenda.

In Maine, six-term Democratic Rep. Mike Michaud, who is running for governor, said he was gay and questioned whether it still mattered to voters, a stark reminder of changing views, lingering resistance to homosexuality and uncertainty about the political implications.

The three potential Republican presidential candidates -- Sens. Marco Rubio of Florida, Ted Cruz of Texas and Rand Paul of Kentucky -- voted against, a reflection that among core Republican conservative voters opposition to gay rights remains strong. No senator spoke in opposition to the measure during Monday's debate.