WASHINGTON - President Barack Obama sought to rally Democratic lawmakers on Wednesday after the loss of a crucial Senate seat, saying it must not weaken their resolve to pass healthcare and financial regulatory reforms.

We've got to finish the job on healthcare. We've got to finish the job on financial regulatory reform, he told members of the Senate Democratic caucus in Washington, echoing similar comments he has made in the past week.

He did not elaborate on how Democrats, who control both houses of Congress, could overcome the loss of a key 60th Senate seat in an election in Massachusetts last month which has stalled his legislative agenda.

The S&P 500 index fell 0.7 percent, led by declines in healthcare and financial stocks, after Obama's comments.

Those two are very policy-sensitive sectors, said Jeff Kleintop, chief market strategist at LPL Financial in Boston. Once again Washington (is) bearing down on the market.

It was the first time Obama had spoken directly to members of the Democratic caucus since the Massachusetts election defeat and his State of the Union address.

With polls showing many Americans unhappy with Obama's handling of the economy and suspicious of his plans to overhaul the $2.5 trillion healthcare system, Democrats face difficult mid-term Congressional elections in November.

Healthcare has become a lightning rod issue in an election year that could hurt Democrats.

If anybody is searching for a lesson from Massachusetts, I promise you the answer is not to do nothing. The American people are out of patience with business as usual. They want us to start worrying less about keeping our jobs and worrying more about helping them keep their jobs, Obama said.

(Additional reporting by Matt Spetalnick in Washington and Edward Krudy in New York; Editing by Eric Walsh)