Yale and its workers opened another chapter in their fitful 40-year relationship Wednesday, as hundreds of union members took their places on campus picket lines in search of higher wages and better pension benefits.

On the same day that Yale opened its doors to upperclassmen, the University’s two largest unions and workers at Yale-New Haven Hospital began a strike at 5:45 a.m. after disagreements on wages, pensions and job security derailed efforts to reach a contract settlement Tuesday.

Union leaders warned the strike – which follows a one-week walkout in March – could last indefinitely if Yale does not make new proposals at the bargaining table.

“Obviously if Yale attempts to dictate a settlement rather than negotiation, it’s going to be a long strike,” Union spokesman Bill Meyerson said.

Union leaders estimated that two-thirds of Local 34, which represents clerical and technical workers, and over 95 percent of Local 35, which represents service workers, participated in the walkout, but University officials disputed those numbers.

Yale administrators said 1,451 of 2,456, or 59 percent, of clerical and technical workers reported to work Wednesday, while only 46 percent reported to work on the first day of the March strike, according to Yale estimates. Yale said 78 of 1,057, or 7.3 percent, of service workers reported to work Wednesday.

“I think it speaks to the obvious point that many workers at Yale think Yale has made a fair and reasonable offer,” Levin said of the attendance figures.

As the strike began and the first students began moving into their dorm rooms, the Rev. Jesse Jackson rallied 700 workers on Beinecke Plaza.

The workers — clad in “On Strike” sandwich boards and chanting “No contract? No work, no peace” — listened to Jackson relate the strike to the abolition of slavery and the civil rights movement of the 1960’s and 70’s.

“In many ways Yale was founded on slavery,” Jackson said as audience members repeated. “It must be saved by bravery.”

The University and locals 34 and 35, which represent nearly 4,000 clerical, technical, maintenance and service workers, began bargaining in February 2002. The two sides did not meet for much of the summer after the last academic year ended but resumed bargaining in mid-August.

Since the two sides resumed bargaining on Aug. 12, Yale and union negotiators have made concessions on some economic contract issues. Union leaders also withdrew their demand that the University recognize the ongoing organizing efforts of graduate students and hospital workers, but the parties agreed that pensions remain the stumbling block.

Local 35 President Bob Proto said the University’s proposals will force people to “retire in poverty.” He said union members should refuse to settle for contracts that do not address their economic concerns.

“Yale and the unions were close on certain issues,” said Jim Foye, a spokesman for New Haven Mayor John DeStefano Jr. “The pension situation was what was holding things up.”

DeStefano, who helped broker a deal between the parties during the last major strike in 1996, urged the sides to come to an agreement.

Eight Yale retirees who said they were concerned about their pension plans staged a sit-in at the Yale investments office Tuesday and demanded an audience with Chief Investment Officer David Swensen.

After the meeting, the workers said they were not satisfied with the way Swensen answered their questions.

“We tried to get him to commit himself morally,” former Yale worker Bill Lewis, 77, told the Associated Press. “He kept repeating that his only function was to manage the investments.”

Meanwhile, managers and students had to fill the void left by the striking workers. Calhoun College master’s aide Lee Ngo ’05 said he and other students are “running the show” while assistants to Master William H. Sledge and Dean Stephen Lassonde participate in the walkout.

Ngo said it has been difficult to cover the responsibilities of his superiors.

Some students moving into their dorms said they took note of the strike, while others said they were barely conscious of the walkout.

“I saw one striker walking by herself on Broadway,” said Vinh Nguyen ’05. “I didn’t even realize [the strike] started today.”

Jackson will speak to striking workers at 11:30 a.m. Thursday, in honor of the 40th anniversary of Dr. Martin Luther King Jr.’s “I Have a Dream” speech. He will also join with striking hospital workers to try and meet with hospital officials at 12:15 p.m. tomorrow.

Union leaders said they are also planning the largest rally in Yale’s history for Labor Day.