* Shooting victim's mother replaces Obama on weekly address
* Speech follows a week of emotional pleas in Washington
Francine Wheeler blinked past her tears, looked straight into the camera and asked Americans to push for tougher gun laws, drawing on courage she said comes from the memory of her 6-year-old son, Ben, murdered in his first-grade classroom in Newtown, Connecticut.
"His boundless energy kept him running across the soccer field long after the game was over," said Wheeler, describing her son during what is usually President Barack Obama's weekly Saturday address to the nation.
"He couldn't wait to get to school every morning," she said, her voice breaking, her husband David beside her, sighing and swallowing hard.
The address was the culmination of a week of emotional pleas in Washington from families of the 26 people killed by a gunman at Sandy Hook Elementary School on Dec. 14.
"To us, it feels as if it happened just yesterday," Wheeler said, recounting the horror of waiting at the firehouse after the shooting "for the boy who would never come home."
The massacre has spurred Obama to propose new restrictions on guns - politically difficult measures in a country where constitutional rights to own guns are defended by powerful lobby groups like the National Rifle Association.
Obama brought the Newtown families to Washington on Monday aboard Air Force One after he gave a speech in Connecticut urging action on his plans.
Obama's proposals to ban more types of military-style assault weapons like the one used in Connecticut and to limit the capacity of ammunition magazines appear to have a slim chance of clearing the Senate.
Even proposals widely supported by Americans - more background checks for gun sales and tougher penalties for gun trafficking - were at risk of faltering.
This week the Wheelers and other families of victims met with senators to urge them to support new laws. On Wednesday Senator Joe Manchin, a conservative Democrat and strong supporter of gun rights, was moved to tears by their stories.
"I feel Ben's presence filling me with courage for what I have to do - for him and all the others taken from us so violently and too soon," Wheeler said in the address, which was broadcast on radio stations and streamed on the Internet.
There were signs of progress this week, she said. Two conservative senators crafted a breakthrough deal to expand background checks, and others backed away from trying to block any debate on the measures.
"But that's only the start," Wheeler said. "They haven't yet passed any bills that will help keep guns out of the hands of dangerous people. And a lot of people are fighting to make sure they never do."
Next week the Senate will begin what is expected to be weeks of debate on gun legislation. The Republican-controlled House of Representatives is waiting to see what the Senate approves before it begins work on the issue.