Cheered by Hollywood stars, President Barack Obama late Saturday lampooned Mitt Romney's wealth and mined a shaggy dog story about his foe, striking a rare light note in the bitter White House race.

Obama used an annual star-studded dinner with White House correspondents and Hollywood A-listers, which presidents use to rip their rivals, to take a few gentle shots at Rommey, before the two rivals face off for the presidency.

He riffed off the hit movie the 'Hunger Games' to poke Romney's hard bore Republican primary approach which he said saw 'wealthy sponsors' brutally savage each other until only one contestant is left standing.

"I'm sure this was a great change of pace for him," Obama joked before a crowd of 2,000 journalists and celebrities.

"Everybody is predicting a nasty election. And thankfully, we've all agreed that families are off-limits," Obama said, after a period when the two campaigns have feuded over the women's vote.

"Dogs, however, are apparently fair game," Obama quipped.

Romney has been dogged by Democratic supporters who keep bringing up the former Massachusetts governor's long-time ago family road trip when he affixed his family pet aboard the roof of his station wagon in a kennel.

As Obama spoke, a large screen in the ballroom of the Washington hotel hosting the dinner, pictured a mock-up of a dog kennel atop Air Force One.

Obama also jabbed Congress which has frustrated his job creation plans and most of the rest of his agenda since Congress seized the House of Representatives in 2010 mid-term elections.

"I've tried to be civil, to not take any cheap shots. And that's why I want to especially thank all the members who took a break from their exhausting schedule of not passing any laws to be here tonight," he said.

The president also took a swipe at a remodelling project in one of Romney's homes in California, quipping that the huge ballroom in the hotel was what his foe would call a 'little fixer upper.'

He also gently ribbed Secretary of State Hillary Clinton, his former Democratic primary rival, who was pictured enjoying a late night drink with friends at the Summit of Americas several weeks ago.

"Four years ago, I was locked in a brutal primary battle with Hillary Clinton. Four years later, she won't stop drunk texting me from Cartagena," Obama said.

And the president, who was embarrassed by a Secret Service sex scandal during a recent trip to Colombia took a gentle swipe at his elite bodyguard.

"I had a lot more material prepared, but I have to get the Secret Service home before their new curfew," he said.

There was no sign of Romney at the dinner, though there were sightings of his combative political aid Eric Fehrnstrom.

The dinner gets blanket media coverage in glamor-challenged Washington DC, which is sometimes mockingly referred to as 'Hollywood, for ugly people.'

It is an annual chance for media and political elites in Washington, a town where those looking for starpower normally have to make do with cabinet members or senators, to rub shoulder with Hollywood's biggest stars.

This year's dinner, the centerpiece of a weekend of parties, will be memorable for political reasons too. Obama had a fine line to tread as he enters a six-month sprint to November's presidential election.

The dinner gave the president the chance to be funny, come across as 'cool' and a free invitation to poke fun at his political opponents.

But at a time when Republicans are again contrasting his 'celebrity' with the plight of Americans still going through economic pain, he might not have much to gain from hanging out with a bunch of Hollywood celebrities.

Last year at the dinner, Obama put on the ultimate show of political sang-froid, ordering the raid that was to kill Al-Qaeda chief Osama bin Laden, then stepping up on stage to wisecrack his way through his speech.

Twenty-four hours later, he would appear on television again -- to announce the successful completion of the Navy SEALs raid deep into Pakistan.

Celebrities at the dinner include reality TV starlet Kim Kardashian, hard partying actress Lindsay Lohan and hearthrob and Oscar winner George Clooney.