Whole Foods Market has again extended its tender offer to buy the outstanding shares of Wild Oats Markets.

Whole Foods has pushed back the deadline to buy up the shares in its fellow US natural and organic retailer to 10 August.

As of the close of business on July 19, 2007, 57.1% of the shares had been tendered and not withdrawn pursuant to the tender offer.

Whole Foods, the US’s largest organic grocer, in February said it planned to buy smaller rival Wild Oats for $18.50 per share, or about $565m.

However, the company is now at loggerheads with the US competition regulator, which is seeking to block the deal on anti-competition concerns.