Yale and union leaders reached a tentative agreement on an unprecedented eight-year contract Thursday, ending a high profile 23-day strike and 19 months of contentious negotiations.

Union leaders will present the agreements to their members today at two separate meetings at the Center Church on the Green. If members ratify the contracts, they will return to work Sunday or Monday, union leaders said. The two sides announced the resolution Thursday at an evening press conference in City Hall, where union and Yale leaders praised the settlement and pledged to develop a better relationship under the new contract.

Negotiators for both sides declined to reveal the details of the proposed settlement Thursday because union leaders wanted to disclose the terms today to workers. But union leaders said they were pleased with the increase in pensions — a major bargaining issue — and Yale leaders touted the length of the contracts,one of the University’s goals in bargaining. The eight-year contracts are the longest ever agreed to by Yale and the unions.

The proposed settlement follows a flurry of bargaining this week after a slow negotiations process in which the two sides often went months without any progress.

But both sides credited New Haven Mayor John DeStefano Jr. Thursday with helping to foster the agreement. DeStefano, who met with the two sides several times since the strike began Aug. 27., played a similar role during the last round of contract talks in 1996, when Yale and its unions settled contracts in his office following two months of strikes.

DeStefano was greeted by cheers and whistling after announcing the tentative agreement to a crowd of students, reporters and community members at Thursday’s press conference. He said he looked forward to helping the two sides forge “a relationship that’s not built on conflict but rather on confidence in each other.”

Levin said he looked forward to having several years without contracts to negotiate so he could improve the relationship between Yale and its unions.

“Every one of those people who are represented by locals 34 and 35 contributes in an important way to the advancement of [Yale’s] mission,” Levin said. “We regard this contract as an investment in those people and thereby an investment in the University’s future.”

The University proposed 10-year contracts in March, maintaining that the extended contract length would give the two sides the chance to build a better relationship outside of negotiations. Because the previous contracts expired in January 2002, the new contracts, if ratified, will expire in 2010.

Union leaders, who had previously lobbied for four-year contracts, said they were also optimistic about the future of labor relations at Yale.

John Wilhelm ’67, president of the parent union of locals 34 and 35, said the two sides were close to an agreement on the eve of the Aug. 27 strike, but had been unable to reach a deal in time. Nevertheless, he said he was heartened by the relative progress since that date.

“I think the real victory here belongs to neither party, but rather to the fact that although we missed on Aug. 26 we have managed to find a common ground after three and a half weeks instead of after many more weeks, as we’ve sometimes done in the past,” Wilhelm said.

Local 35 President Bob Proto said the two sides have negotiated “extraordinary contracts” but that a great deal of work remained to be done.

“They’re contracts that deal with all the basic needs that our workers wanted to have — fair pensions, fair wages, job security — and the hard work really needs to be done in the future to break the cycle of strikes here,” Proto said. “The hard work is to figure out how we can build a foundation and to spring off of that foundation in a new direction.”

The accords came after one of the longest rounds of contract negotiations in the two sides’ historically contentious relationship. Union members’ contracts expired in January 2002, though they were extended monthly until last March. Workers have not received raises since February 2001.

This round of negotiations, which included two strikes and several high-profile rallies, began nearly two years ago, when both sides pledged to reinvent their historically acrimonious relationship. Though they met with a labor-management consultant who urged a friendlier approach to bargaining, talks disintegrated after about three months in May 2002. Since then, the two sides negotiated sporadically as rhetoric became increasingly contentious. Locals 34 and 35 held a five-day walkout in March after several months of threatened strikes.

The two sides clashed over several issues during this round of talks — including pensions, wages, job security and the unions’ demand that the University recognize unionization efforts by graduate students and workers at Yale-New Haven Hospital. The unions dropped the demand for the organizing drives in late August, but pensions, job security in Local 34 and wages remained on the table.

Local 35, which represents Yale’s service and maintenance workers, will hold its membership meeting at noon today. Local 34, which represents clerical and technical workers, will meet at 2:30 p.m.

The 150 dietary workers at Yale-New Haven Hospital, who have been on strike with locals 34 and 35, remain without contracts.