Helicopter builder Sikorsky and the union representing its workers reached a tentative agreement on a new four-year contract Friday night, a company spokesman said.

Spokesman Edward Steadham would not provide any details. A representative of the Teamsters union, whose members must now ratify the pact, was not immediately available for comment.

Hundreds of workers at helicopter builder Sikorsky left in the middle of their shift Friday as talks on a new contract neared a Sunday deadline.

Neither side has commented publicly on the progress of the talks, but the New Haven Register, citing sources close to the negotiations, said the bargaining has not gone as smoothly as hoped.

A union shop steward who would not give his name said the workers were taking half-days and vacation days. A company official said about 1,000 to 1,500 people walked off around 10:30 a.m.

"It looks like maybe half to two-thirds of our first shift," Sikorsky Vice President Matt Broder said.

About two-thirds of the second shift, which starts at 3 p.m., showed up to work, Broder said.

Broder said the company and union negotiating teams were meeting Friday. He said he assumed the departures were related to the contract talks.

The shop steward said the action had not been sanctioned by the union.

A recorded message on a telephone hot line for Teamsters Union Local 1150's said pensions, grievance procedures and mandatory overtime rules were the key issues.

"The pension is it. It's everything," the shop steward said.

The union is seeking an increase in the pension to $3,000 a month, up from the current $1,200, according to sources cited by the Connecticut Post. Broder would not comment on specific dollar amounts and a spokesman for the Teamsters was not available for comment Friday night.

Sikorsky, a division of Hartford-based United Technologies Corp., builds military and civilian helicopters. Models include the Black Hawk and Comanche for the military and the S-76 and S-92 models for civilian, hospital and other uses.

The company is named for Igor Sikorsky, a Russian immigrant whose first helicopter — the VS-300 — completed a 10-second flight on Sept. 14, 1939. The basic design of that pioneering chopper still influences modern design.

Sikorsky has about 3,600 Teamsters-covered workers, most at plants in Stratford and West Palm Beach, Fla.

A strike would be the second such action against a UTC aerospace division in recent months. Machinists union members struck at jet engine builder Pratt & Whitney for 10 days in December.

Workers at the West Palm Beach plant will vote Saturday on any contract proposal. Connecticut members will vote Sunday at the Arena at Harbor Yard in Bridgeport.

Local 1150 began this year with a new leadership team, led by Harvey Jackson. Jackson and other backers of national Teamsters President James P. Hoffa swept the incumbent local 1150 officers from power in November.

Hoffa arrived from Washington this week to help the local union negotiate a new contract, the Register reported.

The previous contract, approved in February 1999, included an immediate raise of 3.5 percent, a 3 percent raise in 2000 and a 2.5 percent raise last year. It also contained an early retirement incentive for a small number of workers.

UTC announced in October that it was laying off about 5,000 workers — about 3 percent of its work force — with most of the cuts falling in the Pratt & Whitney and Hamilton Sundstrand divisions.

At the time, UTC said Sikorsky would be largely exempt from the cutbacks because the helicopter business had remained steady despite the recession.