By Ian Simpson

WASHINGTON (Reuters) - Several hundred rain-soaked Tea Party activists rallied on Saturday to call for the U.S. Supreme Court to repeal President Barack Obama's signature healthcare law after arguments next week.

Speaker after speaker at the two-hour protest in the shadow of the U.S. Capitol tore up copies of the law and condemned it as a threat to American freedoms and a violation of the Constitution.

The flag-waving rally by the Tea Party movement, which fueled a conservative Republican wave in 2010 mid-term elections, was an early start to demonstrations by opponents and supporters of the law around the Supreme Court arguments.

The Supreme Court has scheduled six hours over three days for the arguments from Monday to Wednesday.

"If Obamacare stands, I would have, you would have, future generations would have a future that not even ("1984" author George) Orwell could have foreseen coming," Representative Louie Gohmert, a Texas Republican, told the crowd.

Many activists huddled under umbrellas or wore ponchos against intermittent showers. The rally began with "The Star-Spangled Banner," the Pledge of Allegiance and a prayer, and some Tea Partyers wore colonial outfits.

Speakers repeatedly attacked the healthcare law as socialist and some condemned it as an illegal extension of federal power, just as, they said, Social Security and income taxes had been.

They cheered references to conservative activist Andrew Breitbart, who died this month, and waved signs that said "Keep your politics out of my healthcare" and "Obamacare Unconstitutional."

Herman Cain, who pulled out of the Republican presidential race in December, said the issue before the Supreme Court was not just about repealing the two-year-old law.

"This is about getting our freedom back to just be free to make our own decisions with our lives," Cain said.

The National Federation of Small Business and 26 states are challenging the law, whose key feature requires most adults to buy health insurance. The court is not expected to rule until as late as June 30.

Roger Hardwicke, 52, an engineer from Frederick, Maryland, said the healthcare issue was not a partisan one between Democrats and Republicans.

"It's (between) those that believe in limited government according to the Constitution and those who want to expand the government beyond what the constitution allows," he said.

(Reporting By Ian Simpson; Editing by David Bailey)