"I don't know how much more motivation we need than to see the tears in their eyes and the resolve in their voices," Pelosi said. "To use their grief as a source of strength to help save other people.

"That would start with a vote on bipartisan legislation by Congressman Mike Thompson [D-Calif.], Congressman Peter King [R-N.Y.] and 180 sponsors to expand and strengthen our background checks."

The bill from King and Thompson, H.R. 1565, would expand background checks to cover all commercial firearms sales, including at gun shows. All sales would have to be made through licensed dealers, who would run checks on potential buyers.

As of this week, the bill had 179 co-sponsors, almost all of which are Democrats. But Pelosi said the issue is not partisan, and that the families affected by the Newtown shooting did not visit Congress this week with a partisan agenda.

"They come as Americans who wish to spare their fellow parents and family members the mourning, fear and terror they felt six months ago," she said.

House Minority Whip Steny Hoyer (D-Md.) said that since the Newtown shooting in December, nearly 5,000 other Americans have died due to gun violence.

"This is not just a tragedy, it is an epidemic, one that Congress has a moral responsibility to address," he said.

Rep. Elizabeth Esty (D-Conn.), a freshman lawmaker who has Newtown in her district, said Congress needs to be as brave as many of the teachers who were forced to become first responders when the shooting happened. However, she said Newtown families so far have seen only "inexplicable political cowardice."

"It is shameful that we have not yet had a chance to vote," she said.