WASHINGTON — Sen. Chris Murphy, D-Conn., is the first to admit that the Newtown massacre — and the spate of mass-shootings since then — are propelling his bipartisan bill to overhaul the nation’s “broken’’ mental health system.

But while he also advocates for gun-violence-prevention measures such as expanded background checks, Murphy stops well short of many advocates who say a focus on mental health is a smokescreen intended to divert attention from the real problem — the easy availability and massive quantities of guns in America.

“I understand that many of my friends are worried that moving on mental health reform would forsake the ability to do other things that would reduce gun violence, but I just don’t think that’s the case,’’ Murphy said in a call Thursday with reporters on his Mental Health Reform Act, which he has co-authored with Sen. Bill Cassidy, R-La., who is a physician.

The Murphy-Cassidy bill, which could come up for a Senate vote next year, ramps up mental health treatment to put it on par with that available for physical health. Although mental health parity has been federal law since 2008, psychiatric care often is not accorded equal treatment by health insurers.

About 44 million Americans — including 90,000 in Connecticut — are struggling with mental illness. Among suicide victims, 90 percent have an underlying mental illness.

The National Rifle Association and other gun-rights advocates have focused on mental illness as a solution to the spate of mass shootings from Newtown onward. And at Wednesday night’s GOP debate, N.Y. real estate mogul Donald Trump argued that gun-free zones at schools and elsewhere represent “target practice for sickos and for the mentally ill.’’

Ron Pinciaro, executive director of CT Against Gun Violence, said the Murphy-Cassidy bill would be a “good thing’’ if it succeeds in keeping guns out of the hands of those dangerous to themselves or others.

“It will also be interesting to see if the gun lobby, who claim that mass shootings are a mental health problem and not a gun problem, will support this measure,’’ Pinciaro said. “Don't count on it.’’

Murphy said that while division on Capitol Hill over guns is a political reality, the opportunity for bipartisan movement on mental health should not be overlooked.

“I just come back to the families in Newtown,’’ Murphy said, referring to survivors of the 2012 shooting at Sandy Hook Elementary School that left 20 children and six adults dead. “The families in Newtown want changes in our gun laws, but they don’t want our disagreement over the changes to stop us from moving forward on mental health legislation. That’s, I think, the bottom line for us.’’