Hong Kong urged pro-democracy protesters to pack up their tents and leave their main camp near government headquarters, saying it could not promise there would be no "confrontations" when the site is cleared on Thursday.
Thousands of police will move in on the site in Admiralty, next to the Central business district, after two-and-a-half months of road blockades and sporadic violent scuffles in the former British colony that returned to Chinese rule in 1997.
The protests, which have taken hold on both sides of the harbor, represent the most serious challenge to China's authority since the 1989 pro-democracy demonstrations and bloody crackdown in and around Beijing's Tiananmen Square.
"We can't guarantee there won't be any confrontations," Chief Secretary Carrie Lam, Hong Kong's number two official, told reporters. "I appeal to the protesters who have been illegally occupying our roads to pack up their belongings and to leave the protest sites."
The Admiralty site has stood as a poignant symbol of calls for democracy that have been spurned by the government and Communist Party rulers in Beijing.
"Our aim is to let the world see what we demand and most importantly, that Hong Kongers can unite," said protester Kenneth Kan.
Some were packing up their tents on Wednesday, with some vehicles arriving to take away furniture and supplies. Others scrambled to preserve the "Umbrella Movement" artwork or snapped "selfies" and pictures on phones and cameras.
"I came here sometimes after work but this is the first time for my son," said Alice Leung, accompanied by her nine-year-old. "He has seen the movement on TV but I want him to experience it himself so that he will understand better when he grows up and understand what democracy is."
Many vowed to stay to the end, and the number of protesters swelled as thousands gathered after work and school.
Hong Kong Federation of Students leader Alex Chow said his group and Scholarism, the other main student group backing the protests, were urging everyone who had participated to return to Admiralty on Thursday morning in an act of civil disobedience.
"Some will fight back. Some will sit down and wait to be arrested," said Johnny Chung, a 20-year-old student. "The government is ridiculous. Over 100,000 people came here and slept on the street ... and this government did nothing."
Police sources said clearing the site would begin around 9 a.m. (0100 GMT).
Describing tactics similar to those used to clear another protest site in the Mong Kok district two weeks ago, the sources said workers and bailiffs would first clear the areas subject to the court injunction, then, coming from multiple directions, cordon off the protest area and clear all barricades, tents and people in the roads. They may arrest those who refuse to leave.
Causeway Bay would be cleared after Admiralty, either on Thursday or Friday, the sources said.
Hong Kong returned to China under a "one country, two systems" formula, allowing it some autonomy from the mainland and a promise of eventual universal suffrage.
Beijing has allowed a vote in the next election for leader in 2017 - but insists on screening the candidates first.
The Umbrella Movement, named after the items protesters used to defend themselves from pepper spray and batons, is demanding a fully democratic election with open nominations.
Admiralty is where police fired tear gas at tens of thousands of protesters in late September. That galvanized scattershot protests into a longer-term movement, complete with the democracy-themed artwork and statues, classrooms and food and medical stations.
"We'll be back," proclaimed a large yellow banner hung along one of the pedestrian bridges. "Though we are disappointed, we must not give up hope," said another.
"This movement is incredibly important," said Rose Tang, one of the student activists during the 1989 Beijing protests. "They are making history."
But she urged protesters to depart without bloodshed.
"Don't be a martyr, it is not worth it. Don't try to be a tank man," she said, in reference to a lone man who blocked a line of tanks near Tiananmen Square after the 1989 military crackdown.