Protests against corporate power in the United States has taken root in Washington, with several hundred people occupying Freedom Plaza outside city hall to demand progressive reform.

The Stop the Machine rally - midway between the Capitol and the White House - echoed the demands of the Occupy Wall Street movement in New York that drew more than 5,000 people as well as labour-union support.

"The poor are no long patient," said one of the speakers, Ben Manski, a Green Party activist from Wisconsin, from a stage decorated with the "We the People" preamble of the US constitution.

"It took us long enough, but we are no longer patient," he told the crowd, a mix of young people and middle-aged veterans of protest movements of past decades.

"This is a sacred struggle," on a par with the abolition of slavery, voting rights for women and civil rights, Mr Manski said, "and just like those movements, we are going to win."

The protest got underway just as president Barack Obama told reporters at the White House that the Wall Street protests were an expression of the "frustration" that Americans feel towards the financial establishment.

Since October 1 a separate but like-minded group called Occupy DC has gathered around 30 people daily at McPherson Square on K Street Northwest, where many powerful lobbyists have their offices.

But they were overshadowed by Stop the Machine, which originated a decade ago with opposition to the October 2001 invasion of Afghanistan and the subsequent Iraq war.

No uniformed police were seen at Freedom Plaza as the crowd swelled towards 1,000 around lunchtime under sunny skies. The open square is a frequent venue for political protests.

Several dozen people brought camping gear, planning to sleep on the concrete surface through the weekend at least.

"It is time to light the spark that sets off a true democratic, nonviolent transition to a world in which people are freed to create just and sustainable solutions," said a "call to action" published on Stop the Machine's website.

AFP