ABC News' Jennifer Parker Reports: In a new immigration ad, Former House Speaker Newt Gingrich slams the immigration plan supported by Sen. John McCain, R-Ariz., arguing the legislation would put potential terrorists on a path to U.S. citizenship.
Gingrich -- who has said there is a "great possibility" he will make an '08 bid for the White House -- released the immigration video on his website and to YouTube.
It begins with Gingrich saying, "Mohamed Atta, and several other 9/11 hijackers were in the United States illegally."
Photos of Atta and other 9/11 hijackers appear and the word "Illegally" -- printed in bold, red letters -- flashes over the screen.
"Today, more than five years since that tragic day, our borders remain open to gangs, drug dealers and terrorists," says Gingrich in the ad.
However, a check of the 9/11 Commission Report reveals that Atta entered the United States on a tourist visa and was subsequently approved for a student visa in the days leading up to the attacks.
"Atta was in the country legally on 9/11," confirmed Janice Kephart, a former counsel to the 9/11 Commission and co-author of the commission's report on 9/11 and Terrorist Travel to ABC News.
All of the 19 men who hijacked planes on September 11th, including Atta, entered the United States on a tourist or student visa, issued by the former U.S. Immigration and Naturalization Service, according to the 9/11 Commission.
Atta's visa status was widely reported in the media in 2002 when the INS famously sent a letter to Atta's Florida flight school, which was received on the sixth month anniversary of 9/11. The letter said the INS had approved a request to change Atta's status from a tourist visa to a student visa weeks before the attacks.
However, Gingrich aides defend the ad, saying that some of the hijackers overstayed their visas and lied on their applications.
"Many of them had incomplete or absurd information on their (visa) applications," said Newt Gingrich's spokesperson Rick Tyler.
"Now, you might say that's a stretch that they were illegal, but all of them should have been stopped," he said, "none of them would have gained legal access had their paper work been filed correctly, so I would argue that they were all illegal."
Citizens United, a conservative group lobbying against the immigration bill, paid for the ad and says they have purchased a "six-figure" media buy for the ad to appear on cable television.
In his ad, Gingrich links the threat of terrorism to the immigration debate, arguing against "amnesty" for undocumented workers. The former House Speaker also takes a swipe at McCain's immigration position.
"The new McCain-Kennedy immigration plan will put millions of people who are in our country illegally including potential terrorists and gang members on a path to U.S. citizenship," he says, urging viewers to lobby against the bill.
This isn't the first time Gingrich has taken on his potential '08 GOP rival over immigration. Gingrich criticized McCain two weeks ago, telling reporters the senator's immigration position has hurt his chances of winning the GOP nomination.
"Sen. McCain carries both the burden of McCain-Feingold and now the burden of the McCain-Kennedy bill," Gingrich told reporters following a conference at the American Enterprise Institute in Washington, D.C. on June 8. "He has the greatest challenge in a Republican primary in explaining those positions."