President Barack Obama is expected to make his first public comments today on the growing widening scandal around two of his top generals.

Meanwhile politicians were digging into the tangled tale of emails that exposed one general's career-ending extra-marital affair and the other's questionable relationship with a Florida socialite.

Their main demand was to know if national security had been threatened.

The affair was between David Petraeus, once the top US commander in Iraq and Afghanistan, and his biographer Paula Broadwell, who sent harassing, anonymous emails to a woman she apparently saw as a rival for Petraeus' affections. That woman, Jill Kelley, in turn traded thousands of sometimes flirtatious email messages with current Afghanistan commander Gen. John Allen, possible evidence of another inappropriate relationship.

Petraeus, whose highly respected career led some to speculate on a run for president, resigned his CIA post on Friday, acknowledging his affair with Broadwell and expressing deep regret.

The CIA's acting director, Michael Morell met top Senate intelligence officials to explain the CIA's version of the events that led to Petraeus' resignation. Senators are especially concerned over reports that Broadwell had classified information on her laptop, although FBI investigators say they concluded there was no security breach.

Mr Obama had hoped to use a news conference, his first since his re-election, to build support for his economic proposals heading into negotiations with Congress on the 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 his 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.

Gen. 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 US-led combat operations end in 2014. But Mr Obama put on hold his nomination to become the next commander of US 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.

The FBI decided to turn over the Allen information to the military once the bureau recognised it contained no evidence of a federal crime. Adultery, however, is a crime under the Uniform Code of Military Justice.

Allen, 58, insisted he had done nothing wrong.

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 getting anonymous, harassing emails. They turned out to have been written by Petraeus' mistress, Broadwell, who apparently was jealous of the attention the general paid to Kelley.

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 US official said the emails between Allen and Kelley were not sexually explicit or seductive but included pet names such as "sweetheart" or "dear." While much is relatively innocuous, some could be construed as unprofessional and would cause a reasonable person to take notice.

Kelley served as a sort of social ambassador for US Central Command in Tampa, Florida, hosting parties for Petraeus when he was commander there 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.

Such friendships among senior military commanders and prominent local community leaders are common at any military base.

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