SYDNEY (AFP) - Australian Prime Minister Kevin Rudd on Monday likened rival Tony Abbott's "baddies versus baddies" comments on Syria to a children's game of "Cowboys and Indians", saying he was unfit to deal with foreign policy.

Mr Abbott is the frontrunner to win Sept 7 elections over centre-left Labor incumbent Mr Rudd, with a new poll on Monday showing he has overtaken his rival as preferred prime minister for the first time in four years.

The Newspoll in The Australian showed 43 percent of voters now see Mr Abbott as the better prime minister to Mr Rudd's 41 percent, while his conservative coalition has opened a 54 to 46 percent lead over Labor on a two-party basis.

While Mr Abbott is on track for victory, his diplomatic credentials are being increasingly questioned after he said on Sunday the escalating Syria conflict "is not goodies versus baddies, it is baddies versus baddies".

Mr Rudd said the simplistic language trivialised the matter and mocked Abbott as a graduate from the "John Wayne school of international relations", referring to the legendary movie star who made his name as a gunslinger in Hollywood westerns.

"International relations is more complex than a 1950s John Wayne western," said Mr Rudd, a Mandarin-speaking former foreign minister and diplomat.

He added later: "I mean, the last time I used the term goodies and baddies was when I was playing Cowboys and Indians in the back yard when I was about 10.

"We're talking about serious matters of international security and international relations and the alternative prime minister of Australia is referring to this as no more complex than goodies and baddies or baddies versus baddies.

"These remarks demonstrate that he is not competent and not comfortable with national security and foreign policy."

Mr Abbott, described by Mr Rudd last week as "an exceptionally aggressive and negative politician", defended his remarks, saying: "I've made the point that this is a civil war between two more or less equally unsavoury sides." "I think we're seeing a little bit more hyperventilation from a desperately shrill government," he added.

"Interestingly, people such as David Cameron and Bill Clinton have referred to good guys and not so good guys. I think the odd use of colloquialism is perfectly appropriate if you are trying to explain to the public exactly what the situation is."

His comments came as Australia assumed the rotating presidency of the UN Security Council and as US President Barack Obama launched a lobbying effort to sway sceptical lawmakers as they weigh whether to support military strikes against Syria over a chemical weapons attack on civilians.

While Mr Abbott seems destined to become Australia's next leader, he was keen on Monday to play down the latest opinion poll, warning his rival could never be written off.

"I want to make it absolutely crystal clear, I do not believe the polls," he said.

"Mr Rudd has been a poor prime minister but never forget that he beat John Howard in 2007 and John Howard was the most successful prime minister since Robert Menzies.

"So you've got to respect Mr Rudd's campaigning abilities, even if you don't necessarily have to respect his governing abilities."

In a series of interviews on Monday, Mr Rudd insisted Labor can still win on Saturday.

"We entered this campaign as the underdog, we remain the underdog so let's just call a spade a spade - that's as it is," he told reporters.

"If you're uncertain about what Mr Abbott's putting out there then I think listen to your instincts and don't vote for him".