Jewish groups, working with congressional leaders, are pressing to designate one of the main organizers of the humanitarian flotilla that sought to break Israel’s blockade of Gaza as a terrorist group.

Image by GETTY IMAGES Not Welcome: Rep. Eliot Engel says those on the flotilla should be banned from enter- ing the United States.

With a boost from Senate leaders, the Jewish groups are lobbying the administration to sanction Insani Yardım Vakfı, the nonprofit sponsor of the ship Mavi Marmara. Nine Turkish passengers, including one dual-nationality American, were killed on the Gaza-bound Turkish vessel when Israeli commandos seized control of it in international waters, leading to a clash between the commandos and some of the passengers.

Many questions about what happened on board the ship remain in dispute, and calls for an international investigation have led Israel to sponsor a panel with two international observers that will examine some aspects of the affair, though not what happened on the boat.

But meanwhile, New York-area Congress members and the Jewish Community Relations Council of Greater New York are also urging the administration to deny visas to passengers on the Mavi Marmara who have been invited to speak in the United States about what they experienced.

“The people who were on that flotilla should not be allowed to come to the United States and spill their propaganda and hatred and terrorist rhetoric,” said Rep. Eliot Engel, a New York Democrat. Rep. Jerrold Nadler added: “It is the responsibility of our government to ensure that terrorists, and those who support terrorist activities, not be allowed to enter the United States.”

The twin efforts make up the latest twist in the battle to define the outcome of the high-seas confrontation, which has provoked international condemnation of Israel amid charges by Israel and its supporters that some on the boat were terrorists who sought out the clash to ambush and kill the commandos.

David Letwin, a spokesperson for Al Awda NY, which plans to bring three Mavi Mamara passengers to Brooklyn June 17 to speak publicly, denounced the effort to deny them visas as “a smokescreen.”

‘This has nothing to do with terror,” he said. “It has to do with powerful politicians in this country trying to silence any criticism of what’s going on in Israel.”

In various press reports, Insani Yardım Vakfı, the Istanbul-based Islamic charity known by its Turkish acronym, IHH, has strongly rejected allegations that it is linked to terrorism. Efforts to reach the group for comment on the current push to get it placed on the U.S. terrorism list were unsucessful.

The Anti-Defamation League, in a June 8 letter to Secretary of State Hillary Rodham Clinton, pointed to both the IHH and a coalition of which it is a part, the Union of Good, as groups that should be viewed as terrorist entities alongside Hamas, Hezbollah and Al-Qaeda.

“In light of the extensive connections and significant fundraising activities made by these groups to Hamas, a designated Foreign Terrorist Organization, we would urge the State Department make these two organizations subject to the same restrictions as Hamas,” the group wrote Clinton. In a similar letter, the American Jewish Committee called on the State Department to investigate alleged ties between the IHH and the terror groups Hamas and Al-Qaeda.

In Congress, the demand to investigate the Turkish group came in letters to President Obama from both chambers.

“We recommend that your administration consider whether the IHH should be put on the list of Foreign Terrorist Organizations, after an examination by the intelligence community, the State Department, and the Treasury Department,” stated the Senate letter, sponsored by Majority Leader Harry Reid and Minority Leader Mitch McConnell. The House letter did not call directly for an investigation but points out ties the IHH had with Hamas, which is recognized by the U.S. as a terrorist organization.

Pressure to launch an investigation of IHH has been mounting ever since the May 31 Israeli raid on the flotilla. Reports on the violent nature of the resistance on board the Mavi Marmara triggered an outpouring of information alleging connections between the IHH and acts of terror over the years. But some passengers aboard the ship, including journalists unconnected to IHH or the Free Gaza Movement, its partner in the venture, maintain that it was the Israeli commandos who fired the first shots, using rubber or plastic bullets and stun grenades as they boarded from speedboats and helicopters.

Pro-Israel activists have been pushing for the IHH’s designation as a terror group in open statements and in closed-door conversations with lawmakers and administration officials ever since the clash. For Jewish groups, going after the IHH is one of three main goals set forth in the aftermath of the incident, alongside gaining U.S. support for Israel’s attempts to avoid an international investigation and fighting Israel’s public relations war in American media.

But the strict requirements for designation as a terror organization — and thin evidence proving direct ties between the Turkish group and acts of terror — could make the first goal a lengthy and perhaps impossible undertaking.

The administration has yet to respond to calls to designate the IHH a terror group, although a State Department spokesman told the Forward: “We are aware, however, that the IHH has met with senior Hamas officials in Turkey, Syria and Gaza over the past three years.”

The State Department official didn’t say that IHH ties to Hamas were sufficient reason for designating IHH as a terror group. But in a June 3 press briefing State Department spokesman P.J. Crowley said that such ties were “obviously a great concern for us.”

The IHH was established in 1992 to provide relief to Muslims in Bosnia. It has since grown to become one of the largest Muslim charities, helping causes in 100 countries from Africa to Haiti. In 1996 the IHH was mentioned in a CIA report as one of 15 groups that employed members who had ties to terror groups. But no action was taken against the IHH at the time.

The key to getting a group on the State Department’s list of Foreign Terrorist Organizations (FTOs) is, according to a government official, proving that it “engages in terrorist activity or terrorism, or retains the capability and intent to engage in terrorist activity or terrorism,” and that the group’s activity “threatens the security of United States nationals or national security of the United States.”

Once a group is designated as an FTO, it is illegal for individuals in the U.S. to provide the group with material support of any kind. Individuals who do so can be criminally prosecuted. The group’s representatives are not allowed admission to the U.S., and American financial institutions must freeze any funds belonging to the group.

There are currently 44 organizations on the State Department list, which includes groups such as Hamas, Islamic Jihad and Hezbollah as well as Israel’s Kahana Chai, Ireland’s Real IRA and Peru’s Shining Path.

Groups advocating the designation of the IHH as a Foreign Terrorist Organization are looking at two key elements that they believe help their cause. The first is the IHH’s affiliation with the Union of Good, an umbrella organization of Islamic charities. In 2008 the U.S. Treasury Department designated the Union of Good as one of the “potential fundraising fronts for Foreign Terrorist Organizations.” A Treasury press release stated that the Union of Good was created as a front for raising funds for Hamas. The group, however, was not added to the State Department list.

Evidence dealing directly with the IHH has focused almost exclusively on testimony given by French counterterrorism magistrate Jean-Louis Bruguière during the 2001 trial of Ahmed Ressam, who was convicted of planning an attack on Los Angeles’ international airport as part of the “millennium plot.” Bruguière, the first judge appointed to head French counterterrorism efforts, said in his testimony: “The IHH is an NGO, but it was kind of a type of cover-up.” He claimed that the IHH helped jihadist terror groups obtain forged documents, recruit terrorists and smuggle weapons.

But in a June 2 interview with the Associated Press, Bruguière, who retired in 2007, could not say whether the IHH was still tied to terror organizations.

“They’d have a hard time designating IHH as an FTO,” said Jonathan Schanzer, a former Treasury Department intelligence analyst who dealt with combating terror funding, referring to the State Department. In an interview with the Forward, he said, “Such a designation would not get approved without a fight.” Schanzer, currently vice president of the neoconservative-oriented Foundation for Defense of Democracies, explained that the State Department terror list is comprised of the “best-known terror organizations” and requires evidence of direct involvement in terror. However, including the IHH on the lesser-known Treasury Department list could be “more suited,” according to Schanzer, and no less effective.

Like the State Department list of terrorist groups, the Treasury Department’s list of Specially Designated Global Terrorists includes groups and individuals judged to be involved directly in terror. But it sets a lower threshold by also including groups that “assist in, sponsor, or provide financial, material, or technological support for, or financial or other services” to support terrorism. The Treasury Department’s sanctions against such groups are limited to freezing their assets and blocking their bank accounts. Still, once a group gets included on either list, financial institutions around the world often refuse to deal with it.

Contact Nathan Guttman at Guttman@forward.com