New York: Anti-corporate activists who triggered a national protest movement by occupying a square near Wall Street could not be more focused, except on one little detail: what exactly it is that they want.

After three weeks of permanent demonstration at Zuccotti Park in Manhattan, protesters have astonished doubters and won attention from both President Barack Obama and his Republican opponents with their staying power, organizational savvy and ability to grow.

The core sleeping rough is only a few hundred, but more than 5,000 people streamed through rush-hour traffic last week and smaller branches of the Occupy Wall Street brand are popping up in cities nationwide to protest the fate of the little guy in America, or what they call "the 99 percent."

They use every latest social media tool. They rake in thousands of dollars in donations to buy basic supplies for the camp. By and large they maintain steely discipline when marching so as to avoid provoking the police.

They are in every way the model of a grassroots protest movement - except for that absence of a unified demand.

On Saturday, the start of the fourth week for a protest that initially seemed unlikely to survive a few days, about 1,000 people swarmed away from New York's Financial District to a park further uptown.

The gathering showcased the strengths of the movement.