The City of London Corporation has relaunched legal action against the anti-capitalist protesters camped outside St Paul's Cathedral.
The corporation previously offered to give the protesters until the new year to leave the site.
Stuart Fraser, policy chairman at the corporation, said: "We paused legal action for two weeks for talks with those in the camp on how to shrink the extent of the tents and to set a departure date - but got nowhere.
"So, sadly, now they have rejected a reasonable offer to let them stay until the new year, it's got to be the courts.
"We'd still like to sort this without court action but from now on we will have to have any talks in parallel with court action - not instead."
Earlier today, Occupy Wall Street protesters in a New York park were ordered to leave their encampment because officials said it had become unsanitary and hazardous.
At about 1am local time, police handed out notices from the owner of Zuccotti Park, Brookfield Office Properties, and the city saying that the park had to be cleared.
The City of London Corporation's planning and transportation committee voted today to continue with the legal action.
A notice regarding the decision is expected to be served to the Occupy London movement tomorrow.
Mr Fraser said: "We are getting reports about vulnerable people, cases of late-night drinking and other worrying trends, so it's time to act. It will clearly take time but we are determined to see this through.
"Lawful protesters who stand or walk are a regular part of London. But tents, equipment and now, increasingly, quite a lot of mess, is not what a highway is for and others are losing out."
Notices given to the protesters in New York said the park "poses an increasing health and fire safety hazard to those camped in the park, the city's first responders and the surrounding community".
Protesters were told they could return within hours, but without sleeping bags, tarps or tents.
Occupy London organisers have called for supporters to meet outside the US Embassy in London this afternoon.
Occupy London said in a statement: "As part of the gathering, Americans allied with Occupy Wall Street and Occupy London will demand entry to the embassy to question the ambassador on events happening in New York."
Mr Fraser said City of London Corporation had taken the decision to pursue legal action some time ago, but "where we've had our finger on the pause button, we've now taken it off".
Protesters will be told to remove their tents and equipment within 24 hours. If they remain, proceedings will be issued in the High Court.
Mr Fraser said talks with the protesters made it clear that they "are not going to move any time soon".
He said: "We have a responsibility to clear the highway, which is frankly for the use of everybody."
He added: "We don't have a choice in this."
Mr Fraser said businesses near St Paul's Cathedral have complained about a loss of business and are concerned they will suffer trading losses in the run-up to Christmas.
The Corporation is expecting a legal challenge from the protesters. "I am quite sure their legal teams are on standby," said Mr Fraser.
Court action is likely to take weeks. In a statement, the City of London Corporation said no enforcement action will take place without a further committee debate.
The Corporation's bid does not extend to tents on land belonging to St Paul's Cathedral, which suspended its legal action against the protesters on November 1.
Ronan McNern, a spokesman for Occupy London, said: "It's really sad this is the way the City of London Corporation thought they had to go.
"To be honest, it's really disappointing that they cut off the process of dialogue.
"However, if they want to go down this route we have a legal team who are fully prepared.
"It's significant that the City of London Corporation announced this today just as there have been violent evictions in New York and across the United States."
The chapter of St Paul's Cathedral are meeting tomorrow to consider their response, a cathedral spokesman said.