President Barack Obama says he has seen “no evidence” that former CIA director David Petraeus’ extramarital affair compromised national security.

General David Petraeus’ resignation should be a “sidenote” to his distinguished career, Barack Obama added in his first public comments on the scandal.

The general will testify to Congress about September’s attack on the US consulate in Libya, a top senator says.

Republican senators have called for a joint committee to probe that attack.

Barack Obama declined to say whether the White House should have been informed earlier of the investigation into David Petraeus.

“I am withholding judgment with respect to how the entire process surrounding General Petraeus came up. We don’t have all the information yet,” Barack Obama said.

He added that he had a lot of confidence in the FBI and that they have a “difficult job” to do.

News of the scandal shocked officials in Washington in the immediate aftermath of the US election. Congressional leaders of both parties have said they should have been informed earlier.

Democratic Senator Dianne Feinstein, who chairs the Senate Intelligence Committee, said General David Petraeus, who stepped down on Friday, would give evidence only about the Benghazi attack, in which four Americans were killed.

He would not testify about his resignation over an affair with his biographer Paula Broadwell, she added.

Confirmation that David Petraeus will attend a committee hearing comes after days of reports focusing on the fallout from the revelation that he had an extramarital affair with Paula Broadwell.

After the CIA director’s resignation, it then emerged that Jill Kelley, who filed a harassment report over emails she received that led to the discovery of the affair, was in contact with Marine General John Allen.

The link to General John Allen – currently commanding US forces in Afghanistan and nominated to be the top NATO commander in Europe – prompted the US defence secretary and the White House to stress they have complete confidence in him.

But Leon Panetta requested that Gen Allen’s nomination as Supreme Allied Commander of US and NATO troops in Europe be placed on hold, saying it was the “prudent” thing to do.

General John Allen has denied any wrongdoing and has spoken to Gen Martin Dempsey, chairman of the Joint Chiefs of Staff, to emphasize he is innocent of misconduct, a spokesman for Gen Dempsey said.

David Petraeus could appear before congressional committees as early as Thursday, although no final date for a hearing has been confirmed.

Dianne Feinstein, who chairs the Senate Intelligence Committee, said the general would be asked about the Benghazi attacks, which took place while he was in charge of the CIA.

The attack – initially blamed on a spontaneous protest over an anti-Islamic film – remains a divisive issue in Washington and a focal point of Republican anger.

Arizona Senator John McCain led a group of Republican senators on Wednesday calling for the establishment of a special committee to investigate the deaths of the four Americans, which included the Ambassador Christopher Stevens, in Benghazi.

They said there was need to find out whether there had been a cover-up over the attack, which Senator Lindsay Graham referred to in the same breath as Watergate and the Iran/Contra scandal.

Republicans have also criticized UN Ambassador Susan Rice, after she cited the protests as the reason for the attacks in appearances on US media.

On Wednesday, Barack Obama said Susan Rice had fulfilled her diplomatic duties with “skill and professionalism, and toughness and grace”, and that it was “outrageous” to muddy her reputation.

The president suggested that Republicans had criticized Susan Rice “apparently because they think she’s an easy target”, and said he would co-operate with congressional investigations into what happened in Benghazi.

Meanwhile, acting CIA Director Michael Morell began meetings with legislators in the Senate on Tuesday to answer questions about David Petraeus’ resignation.

Legislators are concerned about a possible breach of national security after it was reported that classified material was discovered on Paula Broadwell’s computer.

However, FBI officials have said the agency concluded in its investigation that there had not been any security breach.

President Barack Obama has made his first public comments on the scandal at a news conference, before meeting business leaders.

His remarks concentrated on his economic agenda and plans for reaching a deal to avoid a package of spending cuts and tax rises known as the “fiscal cliff”.

While David Petraeus attempts to focus on Benghazi, Pentagon investigators are also examining as many as 30,000 pages of Gen Allen’s documents.

They are said to include extensive communication between the general and Jill Kelley, a 37-year-old, married Florida socialite.

The emails are now understood to have included pet names such as “sweetheart” or “dear” but were not sexually explicit or seductive, the Associated Press reports.

In May, Jill Kelley reported anonymous, harassing emails to the FBI. The agency launched an investigation that traced the emails to Paula Broadwell and revealed her affair with David Petraeus.

Jill Kelley has been described as a “social liaison” for the MacDill Air Force Base near Tampa, Florida. Home to the US Central Command, both generals have served at the base in recent years.

The Kelleys are said to have developed close friendships with General David Petraeus and General John Allen, both of whom wrote letters supporting Jill Kelley’s twin sister, Natalie Khawam, in a messy custody battle for her son.

Jill Kelley is known to have thrown extravagant parties for the officers posted there and in August was appointed as an honorary consul representing South Korea, ABC News reports.

It is reported that her Mercedes car displays consular license plates reading “JK1”.

In a recording of a phone call to police on Monday, Jill Kelley asked for diplomatic immunity to have media crews waiting outside her house removed.

“I’m an honorary consul general, so I have inviolability, so they should not be able to cross my property. I don’t know if you want to get diplomatic protection involved as well,” Jill Kelley can be heard saying.

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