One hundred days after the massacre that ended with the death of 20 children aged six or seven in Newtown, Connecticut, it remains unknown whether a gun control bill will be passed in U.S. Congress.

Lawmakers aim to plug the gap that allows gun buyers to circumvent the national background check system. While those purchasing firearms from licensed gun dealers must submit a criminal background check, many buyers can legally purchase guns person-to-person.

But Congress remains bitterly divided and experts said it may be difficult for the two parties to pass a bill.

The Democratic-controlled Senate's new gun control bill includes broadened federal background checks for those purchasing firearms. Senate majority leader Harry Reid said Thursday the gun control legislation would likely be debated in his chamber next month.

Appearing Sunday on NBC's Meet the Press, outspoken gun control advocate, New York Mayor Michael Bloomberg, said he was "cautiously optimistic" that Congress would pass a bill requiring universal backgrounds checks for all gun buyers.

But he said a majority of the public and members of gun rights group National Rifle Association (NRA) said they think there should be reasonable checks before people are allowed to buy guns.

"There are an awful lot of people who think this is one of the great issues of our time," he said.

But host David Gregory noted that Congress is paralyzed, mirroring analysts who say that the GOP-controlled House would not likely pass a bill that gun proponents deemed unfair.

"We will be able to judge that after the recess," Bloomberg countered.

"We're trying to do everything we can to impress upon the Senators that this is what the survivors (of gun violence) want, this is what the public wants, this is what the 900 plus mayors that are in our organization want," he said.

"I don't think there's ever been an issue where people have spoken so clearly where Congress hasn't eventually understood and done the right thing," he said, adding he would buy 12 million U.S. dollars of ads in a new campaign designed to boost support for background check legislation.

Speaking on the same show, NRA head Wayne LaPierre said Bloomberg will not be able to buy votes in favor of what gun advocates describe as government overstepping its boundaries.

"He can't spend enough of his 27 billion dollars to try to impose his will on the American public," he said. "They sure don't want him telling them what self defense fire arms to own."

LaPierre described Bloomberg's comments in recent months as "reckless," saying that he inaccurately describes some firearms as "machine guns."

He noted that universal background checks would do little to curb gun violence, as violent mass murderers are "unrecognizable," adding that the current system of background checks does not include mental health records and that new background checks would simply add to that failed system.

"And they don't prosecute any criminals that they catch. It's a speed bump for the law abiding," he said.

A Quinnipiac University poll taken earlier this month found overwhelming support among U.S. voters for expanded background checks for gun buyers, with other recent polls finding similar results. And 88 percent of U.S. voters favor background checks for those purchasing firearms, while 10 percent oppose such laws.