By Jeff Mason

LOS ANGELES (Reuters) - Democratic presidential contender Hillary Clinton on Friday proposed $70 billion in emergency spending to stave off a possible U.S. election-year recession, upstaging Republican rivals who clashed over the economy but offered few specifics.

The New York senator, who hopes to become the Democratic nominee in the November election, proposed $30 billion to help low-income families hit by the mortgage crisis and $40 billion in other spending, mainly for the poor and unemployed.

The former first lady, trying to build momentum after her narrow New Hampshire primary victory over Illinois Sen. Barack Obama, also urged Congress to prepare an additional $40 billion in tax rebates for low- and middle-income families to be implemented if the initial stimulus fails.

Clinton released her economic proposals amid warnings that a recession is increasingly likely. Federal Reserve Chairman Ben Bernanke hinted on Thursday at "substantive" interest rate cuts and President George W. Bush is considering his own economic stimulus package.

"I don't think we can wait. ... Too many people will be hurt, too many jobs will be lost, too many homes will be foreclosed on," Clinton said, urging the Congress to work with the president to avert a slide toward recession.

Republicans criticized the plan.

"Democrats always look to the government to give away money as the first solution," said Arizona Sen. John McCain, a leading presidential candidate.

Campaigning in South Carolina, McCain said the "most immediate beneficial effect on the economy" could be achieved by making permanent Bush administration tax cuts that are set to expire at the end of 2010.