Two days before British academics were to vote on a possible boycott of their Israeli colleagues, the lines sharpened on Saturday as 600 university teachers from Britain, Canada, the United States and Israel came out in opposition to the move while Palestinian and other academics supported it.

The National Association of Teachers in Further and Higher Education, Britain's biggest union of college teachers, is to vote Monday on a resolution asking its 67,000 members to boycott Israeli colleagues who do not distance themselves from what it calls Israel's "apartheid policies."

The ballot, at the union's annual conference in Blackpool, follows a similar move last year by the smaller Association of University Teachers, with 40,000 members, which first supported a boycott of two Israeli universities, then overturned it. The two unions are set to merge on June 1, but the vote on Monday will determine whether the newly merged union will come into being under the shadow of a dispute over the proposed boycott.

Supporters of the resolution predict it will be approved, but Jon Pike, a philosophy lecturer at the Open University and one of the 600 opponents of the move, said: "I think it's up in the air. I'm not completely pessimistic."