A conservative push to ban gay marriage through a constitutional amendment gained renewed momentum Wednesday after a Senate panel led by Kansas Republican Sam Brownback narrowly approved the measure.

The “Marriage Protection Amendment” would define marriage as a union between a man and a woman, effectively rescinding the Massachusetts law that made gay marriage legal last year.

“None of us takes amending the Constitution lightly,” said Brownback, the chairman of the Senate Judiciary subcommittee on the Constitution.

While a similar effort led by President Bush failed in both chambers of Congress last year, conservative lawmakers are pushing for another vote to head off any decision in the federal courts that could legalize gay marriage.

The measure would need to be approved by two-thirds of those voting in the House and Senate and then be ratified by at least 38 state legislatures.