WASHINGTON (Reuters) - Some Republican senators tried on Friday to craft a compromise bill to impose limited gun restrictions in the face of pressure from Democrats and public rage over the Orlando mass shooting, the deadliest in modern U.S. history.

A gun rights supporter openly carries two pistols strapped to his leg during a rally in support of the Michigan Open Carry gun law in Romulus, Michigan April 27, 2014. REUTERS/Rebecca Cook

A gunman killed 49 people at the Orlando, Florida, gay nightclub last Sunday, sparking a scramble over competing gun measures in the U.S. Senate.

While past gun-control measures have failed to clear Congress, the massacre, coupled with public pressure and a suggestion by Republican presidential candidate Donald Trump that he can work with gun rights lobbyists to bring about change, may be changing the picture.

Republicans over the years have blocked gun control measures saying they step on Americans’ right to bear arms as guaranteed under the U.S. Constitution. During a week-long Senate debate, Democrats generally have criticized proposed Republican measures as being ineffective.

Republicans and Democrats have offered four separate proposals to expand background checks on gun buyers and curb gun sales for people on terrorism “watch lists.” But they seem destined to fail because of partisan politics and a requirement that any proposal muster 60 of the 100 votes in the U.S. Senate.

MAINE SENATOR LEADING EFFORT

Republican Susan Collins of Maine, leading the new effort, is considering a more tailored approach. It would prevent the sale of guns to terrorism suspects whose names appear on either the government’s “no-fly” list, which bans them from boarding planes, or a so-called “selectee” list that requires additional screening at airports, her office said in an emailed statement.

These lists are much shorter than a broad terrorism watch list kept by the FBI.

Collins’ measure also includes a five-year “look-back” provision that would notify the government if someone who had been on the “no-fly” or “selectee” list in the last five years, but was dropped, purchases a gun. “That would allow the FBI to put the individual under surveillance or take other appropriate action it deems necessary,” Collins’ office said.

The gun control issue is deeply divisive and there have been no major restrictions passed since 1994, when Congress imposed a ban on semi-automatic assault weapons. That expired after 10 years.

About 71 percent of Americans, including eight out of 10 Democrats and nearly six out of 10 Republicans, favor at least moderate regulations and restrictions on guns, according to a Reuters/Ipsos poll conducted from Monday to Thursday. That was up from 60 percent in late 2013 and late 2014.

Vice President Joe Biden weighed in on the debate, urging a public groundswell in support of banning the type of weapons that have been used in mass shootings. “Assault weapons and high-capacity magazines should be banned from civilian ownership,” Biden said on Friday.

Both the gunman in the Orlando attack, Omar Mateen, and the married couple who carried out a December mass shooting that killed 14 people in San Bernardino, California, were thought to have been inspired by militant Islamist groups abroad.

PROPOSALS NEXT WEEK

Collins’ proposal likely would be offered in the Republican-led Senate sometime next week, provided the four other gun-control proposals fail to pass on Monday. Collins is working on the legislation with Senator Jeff Flake of Arizona and Kelly Ayotte of New Hampshire; she has also been talking to Democrats.

A senior Democratic aide said that Democrats have concerns that under Collins’ bill, some people credibly suspected of involvement in terrorism would not be covered by the weapons ban.

Collins told reporters on Thursday that barring everyone on terrorism watch lists from weapons purchases carried with it the risk of affecting people who have been swept onto the lists without good cause.

U.S. authorities maintain several watch lists - the Federal Bureau of Investigation maintains three and the Office of the Director of National Intelligence runs one database. People are placed on such lists based on the threat level they are believed to pose.

“What we’re trying to do is not deny constitutional rights to a large group of individuals” who find themselves on watch lists despite the fact that there might not be credible evidence of potential criminal intentions, Collins said.

At least one Senate Democrat, Heidi Heitkamp of North Dakota, has been involved in the talks, her spokeswoman said.

“I think she (Collins) is sincerely committed to finding a way to work this out,” said U.S. Senator Chris Murphy who, along with fellow Democrats, set the U.S. Capitol abuzz by talking on the Senate floor for nearly 15 straight hours this week to demand that Congress act on gun control.

Murphy said it was too early to say whether any Democrats would get on board with her approach.

On Friday, the largest lesbian, gay, bisexual and transgender advocacy group in the United States, the Human Rights Campaign, said it would push for curtailing access to assault-style rifles, expanding background checks for firearms buyers and limiting the ability of suspected terrorists to purchase guns.