UNITED NATIONS — Alarmed at the spread of a Palestinian campaign to boycott Israel and particularly its resonance on college campuses, the Israeli Mission to the United Nations and World Jewish Congress held a conference on Tuesday aimed at galvanizing support for an effective countermessage.

Precisely what that countermessage will be, and how it can successfully be conveyed, were among the goals discussed at the conference, titled “Build Bridges, Not Boycotts,” held at the United Nations headquarters.

Many of the speakers and guests, who included Jewish students, educators and policy experts, agreed that the Palestinian campaign, known as the Boycott, Divestment and Sanctions movement, or B.D.S., had made popular inroads that Israel advocates had failed to stop.

A range of speakers, including Danny Danon, Israel’s United Nations ambassador, and Ronald S. Lauder, the president of the World Jewish Congress, described B.D.S. as a dishonest effort to delegitimize and destroy Israel.