Anti-Wall Street protesters have called a massive pre-dawn show-of-strength to stop police evicting them on Friday from the Manhattan square that is the cradle of their anti-corporate movement. New York Mayor Michael Bloomberg visited the demonstrators in person on Wednesday evening to reassure them that they would be allowed back after a clean-up demanded by the square's owners, but the protesters didn't buy it. In a statement on their website, the Occupy Wall Street movement urged supporters to join them at 6:00 am (1000 GMT) on Friday at Zuccotti Park for "non-violent eviction defense." "Bloomberg says that the park will be open for public usage following the cleaning, but with a notable caveat: Occupy Wall Street participants must follow the rules. These rules include, 'no tarps or sleeping bags' and 'no lying down,'" the statement said. "So, seems likely that this is their attempt to shut down #OWS for good. We won't allow Bloomberg and the NYPD (New York Police Department) to foreclose our occupation." Representatives of owners Brookfield Property descended on the square on Thursday morning with police and dogs, handing out notices to remind protesters that camping and use of tents and other structures was forbidden. About 600 people have been camping out in Zuccotti Park more or less permanently since the occupation was launched on September 17, becoming the epicenter of a movement that has spread to cities across America. The occupation has shown more and more signs of permanence: food stalls have sprung up, an infirmary, an information desk, a video room, even a library. Protesters have no toilet facilities of their own and depend on local restaurants including McDonalds. There have also been reports of locals complaining about demonstrators urinating and defecating in the streets. Brookfield says enough is enough and has set a deadline of 7:00 am (1100 GMT) on Friday for the protesters to begin moving out and let the cleaning begin. "Conditions in the park have deteriorated, presenting health and cleanliness issues which must be addressed," the owners said in a statement. The park "will be reopened to the public for lawful uses consistent with our regulations," the statement said, fueling protesters' fears that something more sinister is afoot. "It's horrible, they want to put and end to this experience. They want to kick us out," said Seth Harper, a 21-year-old protester serving breakfast. "I don't want to be arrested. But I think a lot of people are going to fight." Protesters denied there were any health dangers and said they were fully capable of looking after themselves. "We have sanitation. We have cleaned since the beginning, they should let us do that," said Cynthia Villareal. Facebook groups girded for action and called on supporters to help the protesters conduct their own mass clean-up on Thursday to forestall the need for intervention from the authorities. "Friday morning, we'll awake and position ourselves with our brooms and mops in a human chain around the park, linked at the arms," a posting said. "If NYPD attempts to enter, we'll peacefully/non-violently stand our ground and those who are willing will get arrested." Although the sit-in demonstration in Zuccotti Park numbers only a few hundred people, swelling to several thousand during marches, Occupy Wall Street has struck a powerful note among US politicians and the media. Smaller sister demonstrations have popped up in cities across the country. Bloomberg has pledged to let protesters stay at Zuccotti Park in lower Manhattan's financial district so long as they respect the law, but the movement has already had several run-ins with the authorities. At the end of last month more than 700 protesters were arrested for blocking weekend traffic on the Brooklyn Bridge in New York. Some 700 police in Boston launched one of the biggest crackdowns so far on the movement, arresting 129 protesters for unlawful assembly as they descended on parks in the early hours of Tuesday morning. Former US vice president turned climate-change activist Al Gore became the latest high-profile name to throw his support behind Occupy Wall Street on Thursday. "With democracy in crisis, a true grassroots movement pointing out the flaws in our system is the first step in the right direction," he wrote on his blog (blog.algore.com). "Count me among those supporting and cheering on the Occupy Wall Street movement."