Retired Army Gen. David Petraeus apologized to Congress on Tuesday for sharing classified information with his biographer-mistress, then pivoted from personal to battlefield policy and labeled the current U.S. strategy for fighting Islamic State in the Middle East "inadequate."

In his first public testimony before lawmakers since resigning as CIA director, the former top commander in Iraq and Afghanistan offered the Senate Armed Services Committee his recommendations for how to address problems in the Mideast, which he said unlike Las Vegas "what happens in the Middle East is not going to stay in the Middle East."

He suggested enhanced U.S. support for Iraqi security forces and Sunni tribal and Kurdish fighters. In Syria, he recommended the U.S. take a tougher stance against President Bashar Assad, warning him that if he continues dropping barrel bombs, the U.S. will stop the Syrian air force from flying.

"We have that capability," Petraeus said. "It would demonstrate that the United States is willing to stand against Assad and it would show the Syrian people that we can do what the Islamic State cannot — provide them with a measure of protection."

Petraeus began his testimony by restating earlier apologies for events stemming from his personal life. He was director of the CIA from September 2011 to November 2012, when he resigned after acknowledging an affair with Paula Broadwell, a married U.S. Army reserve officer who met Petraeus while researching a book about his wartime leadership in Iraq and Afghanistan.

"Four years ago, I made a serious mistake — one that brought discredit on me and pain to those closest to me," Petraeus said. "It was a violation of the trust placed in me and a breach of the values to which I had been committed throughout my life."

"There is nothing I can do to undo what I did. I can only say again how sorry I am to those I let down and then strive to go forward with a greater sense of humility and purpose, and with gratitude to those who stood with me during a very difficult chapter in my life."

The retired four-star general was sentenced to two years of probation and fined $100,000 for unauthorized removal and retention of classified information he shared with Broadwell. Members of the committee welcomed Petraeus back to the congressional witness seat and praised his governmental service. A few thanked him for his apology, but their questions were about Iraq, Syria and Iran.

Asked after the committee hearing why he felt he needed to apologize again — he has previously apologized at his sentencing and in other public forums — Petraeus said: "I thought I owed it to this body."

Petraeus warned against rushing to oust Assad without knowing who would fill the resulting political vacuum in the country.

He said he supports setting up enclaves protected by coalition airpower to support moderate Sunnis, give civilians refuge within Syria and provide a place to train additional forces. Republicans have called for buffer zones and some Democratic lawmakers have recently embraced the idea. Petraeus said that while it might not be necessary, he was "not at all opposed to seeing U.S. troops on the ground in an enclave" in an advise-and-assist role.

Petraeus lamented that the U.S. is no closer today to having a moderate Sunni Arab ground force than it was a year ago. Top U.S. military officials say a handful of U.S.-trained Syrian rebels are still on the battlefield fighting the militants — far short of the U.S. goal to train and equip 5,400 rebels a year at a cost of $500 million.

"The central problem in Syria is that Sunni Arabs will not be willing partners against the Islamic State unless we commit to protect them and the broader Syrian population against all enemies, not just IS," Petraeus said. "That means protecting them from the unrestricted warfare being waged against them by Bashar Assad, especially by his air force and its use of barrel bombs."

On Iraq, Petraeus also suggested embedding U.S. advisers down to the brigade headquarters level for Iraqi fighting forces; exploring the use of air controllers with select Iraqi units to coordinate coalition airstrikes; and examining whether U.S. rules of military engagement for precision airstrikes are too restrictive. But he said he was not recommending embedding U.S. personnel at the Iraqi battalion level.

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