PARIS, France — French supermarket retailer Casino's Monoprix arm has started exclusive negotiations over buying online shoe retailer Sarenza, in a deal which Casino said would further reinforce its presence in the online market.

Sarenza generated sales of more than €250 million ($310.30 million) during its last fiscal year, and its planned takeover follows Casino's e-commerce partnership with Ocado, signed last November, as Casino looks to build up the online presence of its Monoprix supermarket unit.

Casino, whose credit rating was cut to junk by Standard & Poor's in March 2016, is under pressure to revive profits in France, its biggest market, where it now makes more than 50 percent of its sales, at a time of slower growth in Brazil, its second-biggest market by revenue.

"By acquiring Sarenza and its expertise, Casino Group will consolidate its position as French leader in urban online retail," said Casino Chairman and Chief Executive Jean-Charles Naouri in a statement.

By Sudip Kar-Gupta; editor: Gopakumar Warrier.