Royal Ahold Delhaize (ADRNY) , the Dutch owner of Food Lion, shares fell sharply in Amsterdam Friday morning, as the supermarket absorbed news that Amazon (AMZN - Get Report) would lower prices at Whole Foods Market (WFM) .

Ahold Delhaize, which also owns Stop & Shop and Hannaford, is seeing pressure on margins in its U.S. division and doesn't expect any margin growth in the second half of the year.

Shares in the Dutch supermarket giant was down 4.22% in Amsterdam, changing hands at €15.77, extending a three month loss of 20.5%.

Whole Foods and Amazon, now moving ahead with their $13.7 billion merger, said Thursday, Aug, 24 that the companies will work to reduce the prices on "a selection of best-selling grocery staples" at the upscale grocer.

"We're determined to make healthy and organic food affordable for everyone. Everybody should be able to eat Whole Foods Market quality - we will lower prices without compromising Whole Foods Market's long-held commitment to the highest standards," Jeff Wilke, CEO of Amazon Worldwide Consumer, said in a statement.

On Monday, Aug. 28, consumers will start seeing lower prices on items including organic bananas, "responsibly-farmed" salmon and organic large brown eggs. Plus, the companies' tech teams are beginning to integrate Amazon Prime into the Whole Foods' point-of-sale system.

In the U.K. Whole Foods products will be available for delivery in 302 postcodes across London and the South East. 

Shares in other supermarkets were also under pressure Friday morning. Tesco (TSCDY) were down 1.76% in the first hour of trading Friday, changing hands at 184.15 pence. Sainbury's (JSAIY) was down 1.25% to 234.55 pence and Morrisons (MRWSY) lost 1.27% to 249.10.

Morrisons, the U.K.'s No. 4 supermarket, has a tie-up with Amazon, which allows Prime Members to get a full delivery within two hours in certain parts of the country.

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