* Protests held at U.S. colleges on Thursday
* Global protests at economic inequality set for Saturday
By Michelle Nichols and Paul Thomasch
NEW YORK, Oct 13 (Reuters) - Protesters with the Occupy Wall Street movement threatened on Thursday to block efforts to clean up the Lower Manhattan park where they set up camp nearly a month ago, raising concerns of a showdown with authorities.
While New York Mayor Michael Bloomberg has said the protests against economic inequality can continue as long as laws are obeyed, the private owner of the publicly accessible Zuccotti Park said the park needs to be cleaned.
Owner Brookfield Office Properties plans to clean the park where several hundred protesters have been sleeping on Friday, a move that demonstrators believe is a ploy to remove them.
"Seems likely that this is their attempt to shut down #OWS (Occupy Wall Street) for good," protesters said in a statement on Thursday. "We know where the real dirt is: on Wall Street ... We won't allow Bloomberg and the NYPD to foreclose our occupation. This is an occupation, not a permitted picnic."
Brookfield Office Properties representatives, escorted by police, handed out notices to the protesters on Thursday to tell them that the park would be cleaned in three stages and would reopen for public use consistent with park regulations.
But the rules ban camping, tents or other structures, lying down on the ground, placing tarps or sleeping bags on the ground and storing personal property -- everything the protesters have been doing since they set up on Sept. 17.
"Brookfield respects the rights of free speech, assembly, and peaceful protest," the company said in a statement.
Police said they will be on hand to ensure public order, but it is up to Brookfield Office Properties to enforce the rules of its park. Police will only become involved if laws are broken or if an official complaint is made by the park owners.
"I'm worried there is going to be a riot," said Lauren DiGioia, 26, who has spent the past week at Zuccotti Park and is a member of Occupy Wall Street's sanitation committee. "It is most definitely a ploy to get us out."
The company said conditions at the park "have deteriorated to unsanitary and unsafe levels," noting there are no toilets in the park.
An accumulation of trash has attracted rodents and neighbors complain of lewdness, drug use, harassment and offensive odors from the protesters, Brookfield said.
Bloomberg, a multi-billionaire and himself a target of protesters who believe the richest 1 percent of Americans don't pay their fair share in taxes, visited the Occupy Wall Street movement on Wednesday night to tell them about the clean up.
"As long as we are nonconfrontational and we cooperate I believe we can do this in a peaceful and orderly manner," said Thomas Leeson, 26, from Charlotte, North Carolina, who arrived at the camp four days ago and is on the sanitation committee.
Protesters are upset that the billions of dollars in bank bailouts doled out during the recession allowed banks to resume earning huge profits while average Americans have had no relief from high unemployment and job insecurity.
The Occupy Wall Street movement has sparked nationwide protests in more than 1,400 cities, according to Occupy Together, which has become an online hub for protest activity.
It also inspired solidarity rallies on Thursday that were due to take place at more than 140 U.S. college campuses in 25 states, according to Occupy Colleges. Some social media photos showed about a dozen or so protesters at various colleges.
According to the website of United for Global Change,there are 869 cities in 71 countries where protests are being planning.
Hundreds of people have been arrested at rallies in New York and police have used pepper spray. Dozens have also been arrested during the past couple of weeks from Boston and Washington D.C. to Chicago and San Francisco.
In Austin, Texas four protesters were arrested on Thursday for criminal trespassing after refusing to leave the protest site when city workers came to clean the area.