A bidder is offering to pay $1,500,100 for a steak lunch with the billionaire investor Warren Buffett, driving the top bid more than $500,000 higher in seven minutes as the annual charity auction on eBay Inc's website heads into the homestretch.

The top bidder, whose identity is being kept anonymous, appears to be a proxy bidder. Such bidders tell eBay in advance how much they are willing to bid, and are automatically awarded the top bid if someone else bids less.

Between 8:33 and 8:40 EDT, a competing bidder submitted six bids, starting at $1 million and then rising in $100,000 increments, only to be topped by the current high bidder, who has the screen name s***l.

The five-day auction ends at 10:30 p.m. EDT (0230 GMT Saturday). The winner and up to seven friends will dine with the world's third-richest person at the Smith & Wollensky steakhouse in midtown Manhattan.

Proceeds benefit the Glide Foundation, a nonprofit in San Francisco's Tenderloin district that offers meals, healthcare, child care, housing and job training for the poor and homeless. Smith & Wollensky is also donating $10,000.

The highest bid in the 11th annual auction remains short of the previous record $2.11 million paid in 2008 by Zhao Danyang, a Hong Kong investor. Wealth manager Salida Capital Corp of Toronto won with a $1.68 million bid in 2009.

Buffett, 79, has built an estimated $47 billion fortune running Omaha, Nebraska-based Berkshire Hathaway Inc , which operates about 80 businesses and has tens of billions of dollars of investments.

The 10 previous auctions have raised more than $5.9 million for Glide. In 2006, Buffett pledged most of his wealth to the Bill & Melinda Gates Foundation and four family charities.

(Reporting by Jonathan Stempel; Editing by Steve Orlofsky)