Members of the Graduate Employees and Students Organization issued an ultimatum to Yale President Richard Levin this morning to grant the group union recognition within one week or face a five-day strike by hundreds of graduate teaching assistants beginning on April 18.

The group’s members will vote on whether to strike at a membership meeting next Wednesday barring a shift in University policy, GESO co-chair Melissa Mason GRD ’08 announced at a press conference this morning in front of the Hall of Graduate Studies. If the vote receives majority support among GESO members, the strike will occur the following week, from April 18 to April 22 — the final week of classes for undergraduates.

GESO’s threat to strike coincides with the release of a petition advertisement in today’s Yale Daily News that was signed by some 300 humanities and social sciences TAs, representing about 60 percent of the University’s 500 humanities and social science TAs, Mason said. GESO claims that an additional 400 non-teaching graduate students in those departments are supporting the group in its quest for unionization, she said.

“President Levin: you have one week — recognize our union,” Mason said at the press conference, which was attended by about 30 GESO members and organizers.

But University officials said they will not alter Yale’s longstanding position against graduate student unionization.

“That position is not going to change, and I think it’s also fair to note that the union that is seeking to organize Yale’s graduate students has never demonstrated that most graduate students favor unionization,” Yale spokesman Tom Conroy said.

Graduate student organizers at Columbia also are moving forward with plans to strike, GESO co-chair Mary Reynolds GRD ’07 said. Graduate TAs at Columbia will vote whether to strike on April 11 and 12 and organizers at both Columbia and Yale are planning to strike the same week.

The strike will be the first multi-campus strike in the Ivy League if approved, GESO organizers said.

“It will be historic,” Reynolds said. “Graduate students have never acted in solidarity before. We’re building a national movement.”

Reynolds said she expects “hundreds and hundreds” of graduate students to attend the April 13 membership meeting, at which all TAs in the humanities and social sciences will vote by secret ballot. Non-teaching graduate students also will be allowed to vote to demonstrate their support for a strike, she said.

In recent months, GESO members have been speaking with graduate students throughout many departments to garner support for a possible strike, Reynolds said. GESO members have cited the shortage of tenured female and minority faculty, unequal pay for professional school students who teach undergraduates, and insufficient childcare among other graduate student concerns that they say the University has failed to address.

But Conroy defended the University’s treatment of its graduate students.

“The fact is that Yale is able to attract the most promising scholars in the world to its graduate program because of the superb educational opportunities it offers, coupled with the very generous financial aid and support that is provided to students,” Conroy said. “That includes the stipends they receive, the tuition fellowships they receive, the health care, and subsidized health care for their dependents.”

GESO, which has gone on strike a number of times during the last 15 years to win recognition from Yale as a union, most recently joined Locals 34 and 35 during a five-day strike in March 2003 and a three-and-a-half week strike that September.