Sen. Susan Collins, R-Maine, is expected to continue her efforts to broker a deal in Congress on gun control legislation in the wake of the mass shooting in Orlando, Florida, last week.

Collins’ spokeswoman said Maine’s senior senator will hold a news conference on the issue Tuesday, after failed efforts Monday by both Republicans and Democrats to advance bills that could tighten federal laws for firearms purchases.

“She wants to do everything she can to help keep guns from terrorists’ hands,” Annie Clark said Monday in advance of Senate votes on the matter. “Negotiations and talks are ongoing as she is attempting to reach a compromise and a path forward.”

Late last week, Collins announced that she would propose legislation to prohibit people on the federal government’s “no-fly” terrorist watch list from buying guns. Collins’ legislation also would apply to people on the “selectee” list, which includes those who have been deemed enough of a terror risk to be subject to additional security screenings before they board airplanes.

Under Collins’ bill, any person who was on either list within the last five years also would be subject to an FBI review if they try to buy a firearm.

“If someone is too dangerous to board an airplane, they’re clearly too dangerous to buy a gun,” Collins has said.

Collins’ proposal would affect about 2,500 Americans, but those people would retain the right to appeal if they believe they’ve been wrongly included on either list.

Even though some on the list have not committed any crimes, Collins said investigators have found enough “credible” information to deem them too dangerous to possess firearms.

Collins’ measure and others like it face opposition from conservative lawmakers who note that a number of individuals have been mistakenly placed on the “no fly” and “selectee” lists, effectively banning them from buying guns and violating their constitutional rights under the Second Amendment.

Federal officials have said Omar Mateen, the man who killed 49 people in a Florida nightclub on June 12, was on the “selectee” list for 10 months in 2013 and 2014.

Collins has supported tightening federal gun laws, but also has said she will continue to oppose legislation offered by U.S. Sen. Dianne Feinstein, D-Calif., seeking to prohibit as many as 1.1 million people – those who have been accused of being terrorists but who have not yet been fully investigated by the FBI – from buying firearms.