WASHINGTON (AFP) -- Protesters from Occupy DC, facing a clampdown on their encampment Monday, stripped down for a topless street party Saturday outside a black-tie gala for Washington's biggest movers and shakers.

President Barack Obama and his wife Michelle topped the guest list for the 99th gathering of the highly exclusive Alfalfa Club, which convenes once a year in a five-star hotel for a lavish dinner and some witty speech-making.

Outside, up to 200 members of the local offshoot of Occupy Wall Street pogo-danced to Twisted Sister's "We're Not Gonna Take It" and Public Enemy's "Fight the Power" as bemused police officers looked on behind barricades.

Leading the revelers were several young women who gleefully bared their breasts, including one who wrote "freedom of expression" on the belly of another. Several men also stripped to the waist despite the winter chill.

But there was a flash of tension as well when some Alfalfa Club invitees passed through the protesters, including one man who found himself in a staring match with a female protester before he was hit with a handful of glitter.

"I'd never heard of the Alfalfa Club before," said protester David Varrows, 64, a Washington artist who turned up in tuxedo, a pig's nose and a sign that read "Brother, can you spare a billion?"

"I guess it's how people mess over America -- they join these clubs and devour whatever they can... It's about who you know, rather than what you know," he told AFP.

Occupy DC set up camp in McPherson Square, two blocks from the White House in the K Street lobbying district, on October 1 to condemn growing inequality and corporate influence over US politics.

Its future is uncertain after the National Park Service said Friday it will enforce a ban on overnight camping in the park, which it owns and polices, from Monday, after tolerating the tent village from the outset.

With about 200 members, the Alfalfa Club meets on the last Saturday of every January, ostensibly to mark the birthday of Confederate war hero Robert E. Lee. It didn't admit blacks until 1974 or women until 1994.

It takes its name from a grass plant -- known in Europe as lucerne -- commonly used to feed cattle.

Current and past members include billionaire investor Warren Buffett, former Federal Reserve chairman Alan Greenspan and astronaut Neil Armstrong, the first man to walk on the moon.