NEW YORK — The small Manhattan square occupied by anti-Wall Street protestors for almost four weeks will be temporarily cleared for cleaning on Friday, New York Mayor Michael Bloomberg said.

Bloomberg went to the protest site, where several hundred people are camped out, to explain the move, which would be the first time the demonstrators are asked to leave, the mayor's office said.

Bloomberg said the owners of the plaza wanted to exercise their duty in cleaning it -- and that this was their right, although protestors would be allowed back immediately.

"Mayor Bloomberg went to Zuccotti Park to talk with the protesters himself and inform them that on Friday morning Brookfield Properties will clean the park," a statement from deputy mayor for operations Cas Holloway said.

"Brookfield has expressed concern about its inability to clean the park and maintain it in a condition fit for public use," Holloway said.

Saying that the mayor was a "strong believer" in the right to free speech, Holloway added: "At the same time, the last three weeks have created unsanitary conditions and considerable wear and tear on the park. This situation is not in the best interests of the protesters, residents or the city."

It was not clear whether this signaled an attempt by the city to clear out the protest, which is being held in a privately owned plaza that the owners are obliged to make available to the public.

Holloway promised "protesters will be able to return to the areas that have been cleaned, provided they abide by the rules that Brookfield has established for the park."

Among new rules posted at the park are a ban on sleeping bags and other camping paraphernalia.