WASHINGTON -- Top national security officials trudged to Capitol Hill on Thursday to grapple with fallout from the David Petraeus sex scandal as Defense Secretary Leon Panetta asked service chiefs to review ethics training for military officers.

Panetta said he was unaware of any other top brass who could be ensnared in the debacle. But citing a string of ethical lapses by senior military officers, Panetta asked the Joint Chiefs of Staff to review ethics training and look for ways to help officers stay out of trouble.

Speaking at a news conference in Bangkok, Panetta also said he has "tremendous confidence" in Gen. John Allen, the U.S. war chief in Afghanistan, whose nomination to take over in Europe is on hold because of suggestive emails turned up in the investigation.

Legislators went ahead with a hearing on the nomination of Gen. Joseph Dunford to become the Afghanistan commander, but put off considering Allen's promotion. Allen had been scheduled to testify.

Sen. John McCain (R-Ariz.) opened Dunford's hearing with kind words for Allen, saying, "I continue to believe that General Allen is one of our best military leaders. And I continue to have confidence in his ability to lead the war in Afghanistan."

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Leading administration officials met privately with lawmakers for a third straight day to explain how the Petraeus investigation was handled and explore its national security implications. Among those appearing before the House Intelligence Committee: Director of National Intelligence James Clapper and Acting CIA Director Michael Morell.

Maryland Rep. Dutch Ruppersberger, the committee's top Democrat, said after the hearing he was satisfied the FBI had behaved properly in not notifying the White House or lawmakers about the inquiry sooner.

Petraeus, the much-honored retired general, resigned his CIA post Friday after acknowledging an extramarital affair with his biographer, Paula Broadwell.

Petraeus told CNN that he had never given classified information to Broadwell. He also said in the off-camera interview, his first since he resigned, that his resignation had nothing to do with his upcoming testimony to Congress about the attack on the U.S. Consulate and CIA base in Benghazi, Libya, that caused the death of four Americans. He told the network he wanted to testify about the Libya matter. He is to appear today before the House Intelligence Committee.

Both Petraeus and Broadwell have said she didn't get any classified documents from him. But the FBI has found a substantial number of classified documents on her computer and in her home, according to a law enforcement official.