By Susan Cornwell and Timothy Gardner

WASHINGTON (Reuters) - Talks intensified in the U.S. Senate on Wednesday on compromise legislation to stop gun sales to people on some terrorism watch lists, as Democrats shut down the House of Representatives to protest their chamber's lack of action.

Several dozen U.S. House Democrats pushing for action on gun control protested on the floor of the House, chanting "no bill, no break!" and demanding that the chamber put off an upcoming recess until legislation is debated.

The protest was the latest move by Democrats to persuade the Republican majority in Congress to take up gun control in response to last week's mass shooting in Orlando, Florida, the deadliest in modern U.S. history.

The Democrats stood or sat at the front of the chamber, where such disruptive tactics are relatively rare. When the presiding House officer, Republican Representative Ted Poe, entered the chamber at about noon EDT (1600 GMT), he declared the House not in order. After banging the gavel several times in an attempt to clear the protesters, he announced the chamber would be in recess and left.

The Democrats remained on the House floor, calling for action before a vacation recess scheduled to start at the end of the week and run through July 5.

Assistant Democratic Leader James Clyburn, likened the push for gun control action to the civil rights movement of the 1960s when sit-ins and other civil disobedience prodded Washington to act on new protections for African-Americans.

Democratic presidential candidate Hillary Clinton tweeted her support for the sit-in, saying, "This is what real leadership looks like."

Democrats in the Senate last week took control of that chamber for nearly 15 straight hours as they called for gun control legislation.

On Monday, the Senate failed to advance four gun measures, including one that would have prohibited gun sales to people on a broad range of government watch lists.

Senators from both parties now are pushing for a compromise. Senate Majority Leader Mitch McConnell said he would schedule a vote on the measure by fellow Republican Senator Susan Collins that would prevent about 109,000 people on "no-fly" and other surveillance lists from purchasing guns.

They were holding private talks on the bill and Collins said it could be voted upon this week.

"We're doing some refinements, reflecting some suggestions that we've had from both sides of the aisle," Collins told reporters. She said one of the issues being negotiated was the question of protecting the constitutional rights of gun buyers.

Senator Orrin Hatch, a senior Republican, said there was a "robust discussion" of the Collins measure but he will not be voting for Collins’ proposal.

"I'm a pro-gun guy," Hatch said.

Senator John Thune, a member of Senate Republican leadership, told reporters: "I think it’s going to get a vote ... whether it can pass or not at this point is kind of a moving target."

The powerful National Rifle Association said it opposes the compromise bill and called it unconstitutional.


House Republicans have declined to advance gun control legislation and House Speaker Paul Ryan said earlier on Wednesday he was "waiting to see what the Senate does" before discussing the topic.

Many House Republicans say they see the problem differently than Democrats. "We don't view the fact that someone becomes radicalized and decides to kill a bunch of Americans ... as a gun problem," Representative John Fleming of Louisiana said on Wednesday. "We view that as a terrorist problem."

The Orlando gunman, Omar Mateen, pledged allegiance to Islamic State during the June 12 rampage in which he killed 49 people and wounded 53 with an assault rifle and pistol at a gay nightclub before being fatally shot by police.

House Democrats frustrated by inaction on guns have staged several actions on the House floor in recent days. They interrupted a moment of silence in honor of the Orlando victims and unsuccessfully sought recognition to bring up bills on expanding background checks and preventing people on "no-fly" and other surveillance lists from buying guns.

Democratic Representative Bobby Rush, in a news conference with House leadership and gun control groups on the steps of the Capitol on Wednesday, recounted his son's 1999 shooting death in Chicago and the mother's primal scream when the doctor said the man had died.

"It's time to end this chorus of primal screams in our nation and the time to end it is now," Rush shouted.

(Reporting by Susan Cornwell and Timothy Gardner; additional reporting by Richard Cowan and Patricia Zengerle; Editing by Bill Trott)