The transit strike that is threatened to begin Friday could cost businesses in the city between $440 million and $660 million a day in lost revenue, according to a legal brief submitted by the city in a state court yesterday.

The brief, filed in Brooklyn on behalf of the commissioner of the city’s Office of Emergency Management, Joseph Bruno, is part of the Bloomberg administration’s legal effort to increase fines for transit workers who may walk off the job. The current three-year contract expires at 12:01 a.m. Friday.

The city comptroller’s office made smaller projections yesterday, estimating that the city’s businesses would lose $1.6 billion in revenue during the first week of a possible walkout. The deputy comptroller for budget, Marcia Van Wagner, said the largest losses of about $400 million would come on the first day, possibly Friday, as commuters and residents cope with a daily routine turned on its head.

“By Monday, people would have figured it out a little more,” Ms. Van Wagner told The New York Sun. While the city’s businesses could recoup lost revenue from the first few days of a strike, if it “extended into Christmas week, that would be a serious problem,” Ms. Van Wagner said.

Not all businesses will suffer. The comptroller’s estimate includes increased revenue that hotels and bicycle stores are expected to earn.

The cost to the city will be greater than lost tax revenue, which is estimated to be between $8.1 million and $12.2 million a day. The legal brief for the Office of Emergency Management detailed what city agencies would have to spend to maintain some level of order if the subways and buses, which carry about 7.3 million passengers during an average weekday, were to come to a halt.

According to the brief, police overtime costs are estimated to be more than $10 million a day; staffing the city’s Office of Emergency Management will cost $70,000 a day; preparing the streets for added traffic will cost the Department of Transportation $142,000 a day, plus additional costs to make sure all cars below 96th Street have four passengers and that no commercial vehicles enter the area between 5 a.m. and 11 a.m.

“You’re going to have to have four in a car, the same way I’m going to have four in a car,” Mayor Bloomberg told reporters yesterday. The mayor said last week that in the event of a strike he plans to sleep on a cot in the office of Emergency Management so he can cross the Brooklyn Bridge to walk to work.

The brief also said school attendance rates could drop to around 46% from 93%. A similar drop occurred during the most recent transit strike, in 1980.

Judge Theodore Jones is expected to decide today whether to rule in favor of the city and issue a preliminary injunction against the union, a move that would make a strike more costly for the union, ratcheting up tensions on both sides.

The union, meanwhile, has filed a countersuit in federal court in Manhattan claiming their right to strike is guaranteed under the First Amendment to the Constitution, according to a union spokesman, Dave Katzman.

The state’s Taylor law prohibits strikes by public employees and docks workers two days’ pay for every day off the job in addition to heavy fines against the union.

Officials from the union and the Metropolitan Transportation Authority began round-the-clock negotiations yesterday evening at 7 at the Grand Hyatt hotel. The rest of the day had been spent in “side-table” negotiations on smaller issues. Late last night, little progress had been made, according to people at the negotiations.

Not all union officials were staying in rooms at the Hyatt, a sign of the divisions within the union that could lead to a transit strike. Dissident members of the union’s executive board, including five vice presidents who want more than union president Roger Toussaint’s demand of 8% a year wage increases for three years, were staying elsewhere.

“He doesn’t want us in the Hyatt so we can’t see what’s going on,” one vice president, John Mooney, said. Mr. Mooney is part of a group seeking a 10% a year wage increases over three years. “Our biggest fear is that there will be some secret deal while were not around.”