Israel’s ambassador to America has canceled his appearance at tomorrow’s Columbia University conference on conflict in the Middle East because of his concerns about the treatment of Jewish students at the university, the embassy announced yesterday.

Hours later, George Mitchell, a former Senate majority leader and chief organizer of the conference, said in a written statement that the gathering at Columbia would be postponed. He did not specifically cite the Israeli envoy’s sudden withdrawal.

“Several government officials – Israeli, Palestinian and American – who had agreed to participate have informed me that they will be unable to attend because they must remain in or travel to the Middle East this week,” Mr. Mitchell, who is a fellow at Columbia’s Center for International Conflict Resolution, said. “As a result, I decided that the conference should be postponed and advised university officials.”

Mr. Mitchell, who helped develop a failed peace plan for the Middle East known as the “Mitchell Report,” said the conference would be postponed until September.

The Israeli ambassador, Daniel Ayalon, had agreed weeks ago to participate in the one-day conference, as part of a panel discussion on prospects for Middle East negotiations. A source at the Israeli Embassy said the ambassador has notified Columbia that Mr. Ayalon is pulling out of the event “in view of complaints by Jewish students of intimidation by faculty members.”

Though the postponement of the conference will probably diminish the impact of the ambassador’s gesture, the decision not to attend the session marks an embarrassing development for Columbia officials, who have made repeated assurances to students, alumni, and Jewish leaders that the university takes seriously the student allegations. While Columbia’s president, Lee Bollinger, has said the university does not tolerate the intimidation of students and intends to investigate the complaints, the ambassador’s pullout reflects the extent to which some American Jewish leaders remain dissatisfied with Columbia’s reaction.

“I don’t think any other act by any other actor could have the same impact as what the ambassador has chosen to do,” Martin Kramer, a fellow at the Washington Institute for Near East Policy and a research associate at the Dayan Center of Tel Aviv University, said. “I hope the alarm bells are ringing loud enough.”

A source inside the embassy said Mr. Ayalon notified Columbia that he would not be participating in the conference after he “consulted with Jewish leaders.”

“Academic freedom is a central pillar of Israeli democracy, and we welcome pluralistic debate,” the embassy source said, reading from a statement prepared for The New York Sun. “However, every effort must be made to ensure academic freedom is not held hostage to intimidation. We eagerly await the completion of the university’s investigation into this matter and trust it will address these concerns.”

The campus controversy over the treatment of Jewish students erupted in October when reports of the student complaints became public. About a dozen students have accused some faculty members in the Department of Middle East and Asian Languages and Cultures of silencing students who expressed opinions in the classroom sympathetic to Israel and using their role as teachers to advance an anti-Israel agenda.

Columbia’s chief reaction to the complaints has been to establish a committee of five faculty members to hear testimony from students and recommend whether to take disciplinary action against any faculty member. The committee says it will complete its work before the scheduled spring break, which begins March 14.

Some Jewish leaders, such as the national director of the Anti-Defamation League, Abraham Foxman, have accused Columbia of taking too long to address the students’ concerns. Some critics also question whether the members of the committee will give students a fair hearing, as a number of them have worked closely with the accused faculty members and have shared their strong criticism of Israel.

Mr. Bollinger was set to deliver the opening remarks to the conference, which was scheduled to take place at Columbia’s Low Library, where the administration has its headquarters. Others who were expected to attend included an assistant secretary of state, William Burns; the Egyptian ambassador to America, Nabil Fahmy, and a Columbia professor, Rashid Khalidi, who occupies the Edward Said chair of modern Arab studies and literature.

Mr. Burns is in the Middle East this week, speaking with Israeli and Palestinian officials. Mr. Ayalon has no plans to leave America this week, according to the embassy.

A Jewish student at Columbia who plans to testify before the Bollinger committee, Bari Weiss, said yesterday in an e-mail message to the Sun that she had hoped Ambassador Ayalon would attend the Mitchell conference and taken a stand “against the neglect of the Administration to provide a safe and free academic environment.”

“However,” Ms. Weiss wrote, “I understand the strong statement he is making. … He is making it very clear that he does not want to be in the presence of a University Administration that has allowed this to go on for so long.”

No date in September was set for the conference.