Microsoft said Wednesday it will reward US Live Search shoppers with cash for purchases, essentially trying to buy market share it tried to win with its failed bid to take over Yahoo. Under the Live Search "cashback" program, shoppers using Microsoft's Internet search service will have percentages of purchases refunded.

Rebate money comes from fees merchants agree to pay Microsoft if Live Search online ads result in sales.

"Our goal is to make Live Search the most rewarding commercial search destination on the Web," Bill Gates said in a release.

The cash back program's more than 700 partners include online auction house eBay, bookstore chain Barnes & Noble and longtime retailer Sears.

The rebate program appears to be part of a fallback strategy by Microsoft in the wake of a failed bid to buy pioneering Internet firm Yahoo for nearly 50 billion dollars (US).

Microsoft wanted to combine online resources with Yahoo to better battle Google, which claims the lion's share of a fast-growing multi-billion-dollar online search advertising market.

Microsoft could put pressure on Google by expanding the rebate program, say by sharing ad revenues with shoppers or letting money accrue for charities or prize pots that people could win.