In what could become a rowdy showdown, a faction of the United Federation of Teachers plans to protest outside the Brooklyn Marriott today, where the delegate assembly will vote on whether to approve a tentative contract reached with the city.

After getting wind of the demonstration, the union leadership is footing the bill for a private security detail to be on hand at today’s closed-door meeting. The local police precinct also plans to post officers outside.

“We are concerned about the democratic process at the meeting and the Brooklyn Marriott Hotel is concerned about how such a large meeting may affect their guests, so they will be hiring an outside security firm to insure order,” the director of staff for the UFT, Michael Mendel, wrote in a letter emailed to teachers.

The monthly delegate assembly meeting, which is typically held at the union’s headquarters in Lower Manhattan, was moved to the Brooklyn Marriott to accommodate the large group of delegates expected to attend.

Some teachers, who are upset they have to “give back” under the proposed contract, are concerned that the union leadership will try to silence their opposition. A chapter leader who teaches at the high school on Rikers Island, Jeff Kaufman, said he is worried that teachers who are not delegates will be barred from the meeting. Only delegates, a group of teachers who represent all city schools, are allowed to cast a vote.

“There are a large number of teachers who have contacted me to express the fact that they want to be there,” Mr. Kaufman said. He is a member of the opposition group, Independent Community of Educators. Teachers holding placards are expected to protest outside the meeting, and Mr. Kaufman has been in email contact with the union president, Randi Weingarten, to ask that all teachers, not just delegates, be allowed inside.

Union officials said yesterday that delegates have first priority and that other teachers will be allowed in on a first come, first-served basis. Space is sure to be tight at the Marriott ballroom, where about 2,000 delegates packed into last month’s meeting when they voted to give the Bloomberg administration an October deadline to settle the contract. If the deadline wasn’t met, they threatened to walk off the job or endorse the mayor’s Democratic challenger, Fernando Ferrer.

Discussion of an endorsement is not on the agenda for today’s meeting.

While the contract is expected to receive the votes needed to pass at the assembly meeting, it will still need the final stamp of approval by the full membership. That vote will be taken as a secret ballot sent to all 100,000 members.

Under the tentative contract, teachers would receive a 15% raise over 52 months in exchange for several work reforms, including returning to work two days earlier and working an additional 50 minutes a week.

After two years of on-again off-again negotiations, Ms. Weingarten and the city labor commissioner shook hands last Monday after seven straight days of talks. Some teachers say the union could have done better. “I wouldn’t deny that teachers need money, there are bills to pay,” an English as a Second Language teacher at the Samuel J. Tilden High School in Brooklyn, John Lawhead, said. “But I’m really more concerned with the concessions.”

A teacher at Norman Thomas High School, Nick Licari, accused the union of sending out the letter about the extra security to intimidate teachers into staying away. Union officials said they were only responding to concerns from the hotel and wanted to ensure everyone’s safety.

Other delegates said yesterday that they were ready to cast a vote in favor of the long-awaited contract.

“It would be such a pity if it does get turned down,” a biology teacher at Health Opportunities high school in the Bronx, Jeffrey Piearsky, said. “When you have to look at the contact overall, we keep tenure, we keep all our rights. I’ve been told by some people that it’s what we’re going to get.”