Supporters said the measure to outlaw the desecration of the stars and stripes was meant to particularly discourage demonstrators burning or otherwise damaging the flag during a protest.

“Freedom of political speech does not include the destruction of a physical object – especially one that thousands of soldiers have sworn and fought to protect,” said House Majority Leader Tom DeLay.

The top House Democrat, Nancy Pelosi, spoke against the measure.

“To truly honor our flag, we should honor what the flag ultimately symbolizes – our commitment to freedom and democracy, including free speech, even speech that we find distasteful,” she said.

The bill now moves to the Senate where its supporters believe it will finally be approved, ending years of rejection.

“It’s going to be really close (in the Senate), within a one or two vote margin,” said Terri Schroeder of the American Civil Liberties Union, which has lobbied against the measure.

It must also be ratified by the states to become law.

The increasingly conservative nature of the Republican-led, 100-member Senate along with a renewed sense of patriotism fanned by the Iraq war have made proponents optimistic.

While supporters argue the legislation is needed to protect a symbol of American democracy, opponents warn it would infringe on the First Amendment guarantees of freedom of speech.

The US Congress has voted repeatedly for such a measure since a 1989. Supreme Court ruling that flag burning was protected as an act of free speech.

The Senate has rejected the proposed amendment in the past, most recently in 2000 by four votes.

Republicans expanded their Senate majority in last year’s elections by four to 55.

To become law, a proposed constitutional amendment must be approved by two-thirds of the House and Senate, and then ratified by three-fourths, or 38, of the country’s 50 states.

Political analysts are predicting a close Senate vote, with lawmakers facing re-election likely to come under pressure to approve it.

“It’s tough to vote against because if you do it’s automatic you’ll face an attack ad in your next campaign,” said Larry Sabato, a political scientist at the University of Virginia.

“The First Amendment is not easy to defend.”