Former. Rep. Gabrielle Giffords, who was critically injured in a mass shooting, delivered the emotional punch to a congressional hearing Wednesday aimed at producing the first significant gun control reform law in nearly two decades.

"Too many children are dying, we must do something," said Giffords, one of 19 people shot in January 2011 by a gunman who had targeted the lawmaker after becoming fixated on her. Six people died of their wounds.

But even Democrats on the Senate Judiciary Committee that heard Giffords acknowledged that an assault weapons ban proposed by President Obama after the Connecticut elementary school shootings lacks the support to pass Congress.

Leading Democratic lawmakers on the committee instead pushed for an expansion of background checks to all gun purchases.

Sen. Charles Schumer, D-N.Y., the third-ranking Democratic leader in the Senate, said a reform bill will have to be bipartisan.

"We can't simply replay the usual zero-sum political game on guns, or the moment will pass us by," Schumer said. He added that widening controls on who can buy a gun may be the best bipartisan solution.

Up to 40 percent of gun purchases are currently not subject to a background check because the transactions are private or take place at guns shows.

"Universal background checks is a proven, effective step we can take to reduce gun violence, and I believe it has a good chance of passing," Schumer said.

But gun control advocates delivered powerful testimony in favor of a tougher Democratic proposal backed by President Obama that would ban many kinds of semi-automatic weapons as well as magazine clips containing more than 10 rounds.

Giffords, who resigned her seat last year to focus on rehabilitation, arrived in the Senate Hart Office Building accompanied by her husband, former astronaut Mark Kelly, who also testified in favor of stricter gun laws.

Giffords now walks with a limp, is blind in one eye and speaks in slow, halting sentences after being shot point-blank in the head at a "Congress on Your Corner" event in Tuscon, Ariz.

Her assailant used a Glock pistol with an extended magazine that contained more than 30 rounds. While the Glock would not be banned under the Democratic proposal, the magazine would be prohibited.

"It will be hard, but the time is now," Giffords testified. "You must act. Be bold. Be courageous. Americans are counting on you."

Republicans argued that the mental health issues, video game violence and lack of school security also contribute to mass shooting tragedies.

Sen. Ted Cruz, R-Texas, contested claims that a gun ban would reduce violence, citing Justice Department statistics. He said such a ban would infringe on the constitutional right to gun ownership.

"Unfortunately in Washington, emotion, I think, often leads to bad policies," Cruz said.

Sen. Lindsey Graham, R-S.C., pointed to the recent story about a Loganville, Ga., mother who defended her family from a home invasion with six bullets.

"Six bullets in the hands of a mother protecting her twin 9-year-olds may not be enough," Graham said.

National Rifle Association Executive Vice President Wayne LaPierre told the committee that background checks would prove ineffective at deterring gun violence, because enforcement of current laws is weak.

"I do not believe the way the law is working now, unfortunately, that it does any good to extend the law to private sales between hobbyists and collectors," LaPierre said.