U.S. President Barack Obama made his first public comments Wednesday on the growing scandal around two of the country's most well-known generals, saying, "I have no evidence at this point that classified information was disclosed that in any way could have any impact on our national security."

Meanwhile, lawmakers dug into the tangled tale of emails that exposed one general's career-ending extramarital affair and the other's questionable relationship with a Florida socialite. Their question: Was national security threatened?

David Petraeus, who resigned as head of the CIA on Friday after admitting an extramarital affair with his biographer, had been set to testify this week before Congress on the Sept. 11 attack on the U.S. Consulate in Benghazi, Libya, in which the U.S. ambassador was killed.

Petraeus has indicated his willingness to testify, the head of the Senate Intelligence Committee, Senator Dianne Feinstein, said Wednesday. No date for the testimony has been set, and Feinstein said the testimony will be limited to the Benghazi attacks.

Flirtatious emails

The 60-year-old Petraeus, whose highly respected career as the top U.S. commander in Iraq and Afghanistan, led some to speculate on a run for president, has expressed regret over the affair with his biographer, Paula Broadwell. U.S. officials say the 40-year-old Broadwell sent harassing, anonymous emails to a woman she apparently saw as a rival for Petraeus's affections. That woman, Jill Kelley, in turn traded sometimes flirtatious email messages with current Afghanistan commander Gen. John Allen, possible evidence of another inappropriate relationship.

A person close to Kelley said Wednesday that the first anonymous email in the case — before Kelley ever received any — was sent to Allen from someone who used the handle "kelleypatrol." Allen forwarded it to Kelley. The person close to Kelley spoke on condition of anonymity because the investigation is ongoing.

That email, which investigators traced to Broadwell warned Allen to stay away from Kelley. In the email, the writer said she knew Kelley and Allen had a meeting scheduled.

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Retired general David Petraeus, left, co-authored his biography All In: The Education of General David Petraeus with Paula Broadwell, right. (ISAF/Associated Press)

Meanwhile, word surfaced that Kelley's pass to enter MacDill Air Force Base in Florida, for which she had served as a kind of informal social ambassador, had been indefinitely suspended. Pentagon spokesman Lt. Col. Steven Warren said she can still enter the base but now must report to the visitor centre and sign in like anyone else.

Separately, Broadwell, who is a West Point graduate and a former army intelligence officer, had her security clearance suspended, a U.S. official said. Because her clearance was issued through the army, it was the service's move to suspend it.

Security clearance suspended

It's not unusual for someone's clearance to be suspended if that person is under investigation, particularly in cases of possible security breaches.

The official was not authorized to speak publicly about the clearance so requested anonymity.

As for Petraeus, Obama said he did not want to comment on the specifics of the investigation, and he said he hoped the scandal would be a "single side note" in the retired general's otherwise extraordinary career.

Obama brushed aside questions about whether he was informed about the FBI investigations that led to the disclosures quickly enough. "I have a lot of confidence generally in the FBI, and they have a difficult job," he said. "It's best right now for us to see how this process unfolds."

The FBI's Director Robert Mueller and Deputy Director Sean Joyce met with Feinstein and the House Intelligence Committee. Acting CIA Director Michael Morell went before the House panel next.

The lawmakers are especially concerned over reports that Broadwell had classified information on her laptop, though FBI investigators say they concluded there was no security breach.

Obama had hoped to use Wednesday's news conference, his first since his re-election, to build support for his economic proposals heading into negotiations with lawmakers on the so-called fiscal cliff — the year-end, economy-jarring expiration of tax cuts Americans have enjoyed for a decade, combined with automatic across-the-board reductions in spending for the military and domestic programs.

But the scandal threatens to overshadow Obama's economic agenda this week, derail plans for a smooth transition in his national security team and complicate war planning during a critical time in the Afghanistan war effort.

Allen stays in job

Allen has been allowed to stay in his job and provide a leading voice in White House discussions on how many troops will remain in Afghanistan, and for what purposes, after U.S.-led combat operations end in 2014. The White House said the investigation would not delay Allen's recommendation to Obama on the next phase of the U.S. troop drawdown from Afghanistan, nor would it delay the president's decision on the matter. Allen's recommendation is expected before the end of the year.

But Obama put on hold Allen's nomination to become the next commander of U.S. European Command as well as the NATO supreme allied commander in Europe, at the request of Defence Secretary Leon Panetta, until Pentagon investigators are able to sift through the 20,000-plus pages of documents and emails that involve Allen and Kelley.

NATO Secretary-General Anders Fogh Rasmussen said Wednesday that he had "full confidence" in Allen and looked forward to working with him if he is ultimately confirmed.

The FBI decided to turn over the Allen information to the military once the bureau recognized it contained no evidence of a federal crime, according to a federal law enforcement official who was not authorized to discuss the matter on the record and demanded anonymity. Adultery, however, is a crime under the Uniform Code of Military Justice.

Allen, 58, insisted he'd done nothing wrong and worked to save his imperiled career. He told Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, that he is innocent of misconduct, according to Col. David Lapan, Dempsey's spokesman.

At a news conference Wednesday in Perth, Australia, Panetta said, "No one should leap to any conclusions" and said he is fully confident in Allen's ability to continue to lead in Afghanistan. He added that putting a hold on Allen's European Command nomination was the "prudent" thing to do.

Known as a close friend of Petraeus, Kelley, 37, triggered the FBI investigation that led to the retired four-star general's downfall as CIA director when she complained about receiving anonymous, threatening emails. They turned out to have been written by Broadwell, who apparently was jealous of the attention Petraeus paid to Kelley.

'Inappropriate communications'

In the course of looking into that matter, federal investigators came across what a Pentagon official called "inappropriate communications" between Allen and Kelley, both of them married.

A senior U.S. official told The Associated Press that other senior U.S. officials who read the emails determined that the exchanges between Allen and Kelley were not sexually explicit or seductive but included pet names such as "sweetheart" or "dear." The official said that while much of the communication — including some from Allen to Kelley — is relatively innocuous, some could be construed as unprofessional and would cause a reasonable person to take notice.

That official and others who described the investigation requested anonymity on grounds that they were not authorized to discuss the situation publicly.

Kelley hosted parties for Petraeus when he was commander at U.S. Central Command in Tampa, Fla., from 2008-10. Her and her husband's friendship with Petraeus began when he arrived in Tampa, and the Kelleys threw a welcome party at their home, a short distance from Central Command headquarters, introducing the new chief and his wife, Holly, to Tampa's elite, according to staffers who served with Petraeus.

On Capitol Hill, lawmakers said they should have been told about the investigation earlier. Morell, who took over Petraeus's duties at the CIA, met with Feinstein and ranking Republican Senator Saxby Chambliss on Tuesday.

Asked by reporters if there was a national security breach with the Petraeus affair, Feinstein said, "I have no evidence that there was at this time."

The Senate Armed Services Committee planned to go ahead with Thursday's scheduled confirmation hearing on the nomination of Marine Corps Gen. Joseph Dunford, who is to replace Allen as commander of U.S. and NATO forces in Afghanistan, if Allen is indeed promoted to the European Command post.

In a statement released through his lawyer Wednesday night, Allen says he will "fully co-operate" with the investigation ordered into communications he had with Kelley, and that he instructed his staff to do the same.

The lawyer, Col. John G. Baker, says Allen wants questions in the probe resolved as quickly and completely as possible.