WASHINGTON (AFP) - President Barack Obama was confronted by the scandal that has rocked the US security establishment Wednesday as he prepared his first news conference since the fall of CIA chief David Petraeus.

Obama, also facing the press for the first time since re-election, was to speak amid mounting pressure from lawmakers for answers and after the scandal over Petraeus’ extra-marital adventures snared another top general.

The widening probe into Petraeus’s behaviour raised questions about the US commander in Afghanistan, distracting from talks over a looming budget crisis and on filling high-level positions in Obama’s second term. The White House expressed confidence in John Allen, after the four-star general was linked to the scandal, which saw Petraeus resign in disgrace after a sterling career just three days after Obama’s re-election. Allen was placed under investigation after FBI agents probing email threats sent by Petraeus’ mistress stumbled upon a vast trove of messages Allen sent to another married woman at the heart of the scandal.

According to Pentagon officials, the married general denies having had any sexual liaison with 37-year-old Tampa socialite Jill Kelley, but the volume of flirtatious correspondence could amount to “conduct unbecoming an officer.”

Allen had been due to face lawmakers this week for a hearing to confirm his promotion to the post of Nato’s supreme commander in Europe, but Obama has put his career on hold until the Pentagon completes its investigation.

“The president thinks very highly of General Allen and of his service to his country, as well as the job he has done in Afghanistan,” White House spokesman Jay Carney told reporters.

Petraeus resigned last week when it became clear his affair with 40-year-old military reservist Paula Broadwell, who travelled to Afghanistan to write a fawning biography of him, would become public.

FBI agents stumbled on the liaison after a complaint from Kelley - a close friend of both Petraeus and Allen - who told a federal agent she had received threatening emails, which investigators later traced to Broadwell. The emails she had sent to Kelley - who told investigators she did not know Broadwell - suggest the biographer was jealous of the socialite’s rapport with generals at US Central Command in Florida.

US media reported that Broadwell had criticized Kelley to senior generals under the online pseudonym KelleyPatrol, including one mail to Allen in which she called Kelley a “seductress.”

Broadwell was photographed on Wednesday in Washington, staying at her brother’s house, but has not addressed the media scrum camped outside.

The Pentagon is meanwhile investigating Allen after FBI agents found he had sent hundreds of emails to Kelley. He has denied having a romance with her.

Petraeus and Broadwell were interviewed by investigators and both admitted to the affair, which the retired four-star general told friends he ended about four months ago.

Petraeus had been due to testify to Congress this week on the September 11 assault in Benghazi, Libya that killed four Americans, including US ambassador Chris Stevens and two former Navy SEALs working for the CIA.

Democratic Senator Dianne Feinstein told CNN she expected Petraeus would agree to testify at a later date, adding that she had seen nothing to link the scandal to Benghazi. Fox News said he would appear on Friday.

Meanwhile, in letters to FBI chief Robert Mueller and Attorney General Eric Holder, House Judiciary Chairman Lamar Smith expressed concern over the failure to notify key administration officials earlier.

Petraeus took command of the CIA 14 months ago, retiring from the military after a storied career in which he commanded troops in Iraq and Afghanistan.

The general, who presided over the 2007 troop “surge” in Iraq, is widely credited with turning the tide of the US war there, though his efforts were less successful in Afghanistan.