Kroger boosted its investment in Ocado by 5 percent and said it will work exclusively with the web-based British grocery to boost online products in the U.S.

The move comes as e-commerce giant Amazon expands aggressively into the grocery business. The company acquired Whole Foods Market last year and launched a two-hour grocery delivery service through its Prime program. Rival Walmart, meanwhile, said Thursday that online grocery orders helped boost quarterly sales to $77.7 billion.