United Nations Secretary General Ban Ki-moon urged Israel on Tuesday to agree to international participation in an investigation into its deadly raid on a Gaza-bound aid flotilla.

UN associate spokesman Farhan Haq said Ban wants to underscore that "credible international involvement is crucial to a prompt, credible, impartial and transparent investigation" that the Security Council called for after Israel's May 31 raid that killed eight Turks and a Turkish-American.

"The secretary general understands that Israel is still considering how and if to bring an international element into the investigative process," Haq said.

Israel's Vice Prime Minister Silvan Shalom said Monday the government is considering the options for an investigation and is dealing with the United States and the United Nations. He told The Associated Press that "a decision will be published in a short time."

Iranian President Mahmoud Ahmadinejad salutes the media with a clenched fist in Istanbul, Turkey, Tuesday. Ahmadinejad called the Security Council the most un-democratic body of the United Nations. (Vadim Ghirda/Associated Press)

The Palestinians and Arabs are insisting that the investigation be "independent." But Israel's U.S. ambassador objected to such an inquiry, believing the international community is biased and that it is capable of investigating the incident itself.

An Israeli Foreign Ministry official said Sunday that Ban was moving ahead with plans for an international commission that would include Israeli, Turkish and U.S. representatives.

The UN chief wants former New Zealand prime minister Geoffrey Palmer, a maritime law expert, to head the panel, the official said, speaking on condition of anonymity because Ban has not announced details of his proposal.

Investigation likely to be high on meeting agenda

The investigation is expected to be high on the agenda of a meeting Wednesday afternoon between Israel's Foreign Minister Avigdor Lieberman, who flew to New York on a long-planned visit, and Susan Rice, the U.S. ambassador to the UN.

Israeli forces rappelled from helicopters onto the six vessels in the international aid flotilla on May 31 to prevent them from breaking an Israeli blockade of Gaza, imposed in 2007 after Hamas overran the territory.

There was no violence on five of the ships but video footage from the Israeli military and Turkish TV showed passengers attacking the Israeli soldiers descending on ropes onto a Turkish ship with metal bars.

Israel claims its troops acted in self-defence against the attackers. Activists and their supporters say Israeli commandos needlessly opened fire.

A preliminary autopsy report released by Turkey on Saturday said the nine men killed were shot a total of 30 times.

The Israeli military said Tuesday it has set up an internal team of experts to examine last week's raid on the flotilla. The military said the team would review various internal investigations already going on and expects some findings by July 4.