A U.S. lawmaker wants the Federal Aviation Administration to investigate allegations that Delta Airlines has entered into an agreement with Saudi Arabia that would prohibit American Jews from flying into the country, calling it a direct violation of the Constitution.

"I request your investigation into this matter to determine whether Delta Airlines violated U.S. law or regulation and to ensure no U.S. citizen is denied their right to fly solely on the basis of their religion," Illinois Sen. Mark Kirk wrote in a letter to the head of the FAA.

The call for an investigation came as Delta responded to outrage about Saudi Arabian Airlines joining SkyTeam Alliance - of which Delta is a member. SkyTeam is a 14-member international airline alliance based in Amsterdam.

Delta strongly refuted allegations it was discriminating against Jews or Christians, explaining that they are required to follow "all applicable laws governing entry into every country we serve."

"Delta does not discriminate nor do we condone discrimination against any of our customers in regards to age, race, nationality, religion or gender," said spokesman Trebor Barnstetter in an email to Fox News Radio.

But critics say Saudi Arabia does - preventing passengers holding Israeli passports or passports with Israeli stamps from entering the country. The Religious News Service reported that religious items like Bibles can be confiscated at Saudi Arabian airports. And women must adhere to strict Islamic dress codes.

"Delta's only agreement with Saudi Arabian Airlines is a standard industry interline agreement, which allows passengers to book tickets on multiple carriers, similar to the standard interline agreements American Airlines, US Airways and Alaska Airlines have with Saudi Arabian Airlines," Barstetter wrote. "Delta does not intend to codeshare or share reciprocal benefits, such as frequent flier benefits, with Saudi Arabian Airlines, which we have confirmed with SkyTeam."

The Saudi Arabian Embassy in Washington told Fox News Radio they welcomed the investigation and called allegations that Jews are not allowed into their country "complete nonsense."

"It will put to rest these rumors that we discriminate," said embassy spokesman Nail Al-Jubeir. "The fact of the matter is American citizens are not being discriminated against based on their religion. "Anybody who tells you they've been denied a Visa because they're Jewish, call me and we'll look into it."

So if a Jewish passenger boards a flight in the United States bound for Saudi Arabia, would they be allowed to board the jetliner? Delta Airlines did not return telephone calls or an email requesting comment.

Jay Sekulow, with the American Center for Law and Justice, said eventually Delta will have to answer 'no' to that question.

"Saudi Arabia won't issue the passport," Sekulow said. "The reality is if you've got Israel stamped on your passport and you're not Jewish you're not getting a Visa. In effect, whatever Delta wants to say, they're enforcing that policy."

"You can't let a U.S.-based company who has a U.S. license to benefit in an economic transaction from a group that is basically violating U.S. Human Rights law based on religion," he added.

The Anti-Defamation League issued a statement calling for Delta and other American airlines to make clear that it would "not be a party" to discriminatory policies against Jews and Israelis.

"Delta should not be enabling that kind of discrimination," said Michael Salberg, director of international affairs for the ADF, noting that their concern is not with Delta's policies, but indirectly because of the policies of the Saudi government.

"We are concerned about the potential that such an alliance would have for discriminating against Jews and members of other religions," he said. "The Saudi government has a longstanding policy of religious and other forms of discrimination. Jews are effectively banned from entering the country."

Abraham Foxman, the national director of the ADL, wrote a letter to Delta stating, "We expect Delta, and any other airline which flies to Riyadh or partners with an airline that flies there to ensure that its passengers - whatever their faith - not be discriminated against, and that no American airline in any way enable, or facilitate this discrimination, whatever the regulations of Saudi Arabia."

Among those outraged is Jeffrey Lovitky, a Washington, D.C.-based attorney. Hs sent letters to Delta's board of directors asking them to obtain assurances from the Saudi government that no passengers on any code-shared flight with Delta would be subjected to discrimination on the basis of their gender, religion or other prohibited grounds.

"This is a matter of deep principle," Lovitky told Fox News Radio. "This involves whether an American airline should be permitted to form an alliance with a partner which is engaged in the most blatant forms of discrimination against individuals on the basis of their religion and their gender."

Lovitky, who is Jewish, said the partnership should be an affront to Americans of all religious backgrounds and he won't be a passenger on Delta until they end the partnership.

"It sends a message to Jewish Americans, Christian Americans, female Americans - it sends a message that we put our profit interests before we up our commitment to basic human rights and basic American values," he said. "And that, sir, is fundamentally wrong."

Delta released a statement from SkyTeam explaining they are trying to grow its business in the Middle East and the partnership with the Saudis is part of that strategy.

"Visa requirements or other possible government travel restrictions to enter any country are dictated by that nation's government, not the national airlines or foreign carriers," the statement read. "These requirements apply to anyone entering the country either by land, air or sea.

Lovitky said he understood the economics involved, but, "They are an American airline and they should be expected to adhere to what we consider to be decent and appropriate conduct."

"They need to say this is not a route worth risking our reputation over," Sekulow said, suggesting the airline entered into the agreement not realizing the repercussions. "Delta is not compelled to do business with Saudi Arabia."

Delta said SkyTeam members voted to include Saudi Arabian Airlines into the alliance. However, the airline would not say if any concerns were raised about the Saudis or how Delta voted.

Saudi Arabian Airlines is scheduled to officially join SkyTeam in 2012.