In withdrawing the invittation, the rally sponsors, The National Coalition to Stop Iran Now, and the Conference of Jewish Groups said (via Politico):

(New York, Sept. 18, 2008) --- The purpose of “THE RALLY TO STOP IRAN NOW” on Monday, Sept. 22, 2008, is to protest the presence of Iran’s President Ahmadinejad at the United Nations, and to oppose his nuclear weapons program. We take most seriously his threat to wipe the United States and Israel “off the map” and believe the world leaders gathered at the United Nations must act with resolve to prevent a nuclear armed Iran that would be a threat to this country, Israel and the world.

For this reason, tens of thousands of people of every faith and ethnicity are expected to hear messages from prominent religious and civic leaders, including Nobel Laureate Elie Wiesel and Israeli Knesset Speaker Dalia Itzik. In order to keep the focus on Iranian threats and to ensure that this critical message not be obscured, the organizers of the rally have decided not to have any American political personalities appear.

This issue, opposition to a nuclear-armed Iran, is one which enjoys bipartisan support and the backing of the American people across the political spectrum. On this, all Americans stand together. We acknowledge and deeply appreciate those American political leaders who have been and remain prepared to stand with us as we collectively address the dangers of Iran's nuclear program and its support for terrorism globally.

We hope that the world leaders gathered at the UN will hear this message and resolve to act decisively against the Iranian nuclear program by implementing UN and Security Council resolutions and sanctions.

We again call on all concerned Americans of every background to join us at the "RALLY TO STOP IRAN NOW" on Monday, Sept. 22, at 11:45 A.M.

Signed:
The National Coalition to Stop Iran Now
The Conference of Presidents of Major American Jewish Organizations
United Jewish Communities
UJA-Federation of New York
The Jewish Council for Public Affairs
The Jewish Community Relations Council of New York