SYDNEY (AFP) - She might be one of the most powerful women in the world but that did not wash with security at the G20 in Sydney who reportedly asked Ms Janet Yellen to show her ID.

The head of the United States Federal Reserve was stopped on Saturday as she entered a restaurant at the Intercontinental, one of the host hotels for the weekend summit of finance ministers and central bankers.

Wall Street Journal international finance reporter Ian Talley, who was close by, said the central bank chief had to rifle through her purse to produce her credentials.

"Arguably world's most powerful woman, but Fed's Yellen isn't a celeb yet: #G20Australia staff just ask her for ID to enter breakfast," he tweeted.

G20 officials are meeting throughout Saturday and Sunday with the Fed's winding back of its monetary stimulus policy a key topic.

Ahead of the meeting, Ms Yellen met two suburban small business owners, invited by Australian Treasurer Joe Hockey as part of his plan to keep the world's top officials in touch with the man on the street.

"We plucked them out of the phone book effectively and said 'Come along and meet Dr Yellen'," Mr Hockey said.

"(It was) drawing the link between the most powerful central banker in the world - someone who has the global economy in their hands - and someone on the ground making furniture or running a little tourism business.

"That's what it's about. We're all working for those people."

Ms Yellen, who is attending her first G20 finance ministers summit since replacing Mr Ben Bernanke, reportedly said: "It was nice to meet them."