WASHINGTON (Reuters) - President Barack Obama on Wednesday is expected to be grilled about negotiations to avert a looming "fiscal cliff" and the scandal that brought down CIA director David Petraeus when he holds his first news conference since winning a second term.

Obama will have little time to savor his decisive November 6 victory over Republican Mitt Romney as he takes questions from the White House press corps for the first time in months in an encounter in the ornate East Room, starting at 1:30 p.m. EST.

The White House had hoped to use the news conference to mobilize public support for Obama's economic agenda in the face of a showdown with congressional Republicans over an economy-shaking package of tax increases and deep spending cuts set to kick in at year-end unless a deal is reached.

But instead a heavy focus will be on Obama's first words on a scandal over an extramarital affair that cost Petraeus his job and has expanded to include the top U.S. commander in Afghanistan, Marine General John Allen, who is being investigated for "flirtatious" emails with a woman at the center of the case.

The scandal, which erupted late last week, complicates Obama's efforts to reorganize his national security team following his re-election.

Obama also is likely to face tough questions about where he sees grounds for compromise with Republicans on taxes and spending, how he plans to remake his Cabinet and where he is heading with his second-term foreign policy agenda, including Syria, Iran, China and the war in Afghanistan.