NEW YORK (Bloomberg) — Amazon.com Inc. is near an agreement to buy Quidsi Inc., the owner of Diapers.com and Soap.com, for $540 million, two people with knowledge of the matter said.

An announcement may come as soon as today, said one of the people, who declined to be identified because the deal isn't yet public.

Quidsi, which expects to ship 500 million diapers this year, will help Amazon cater to new parents and gain expertise in warehouse management and low-cost shipping. Amazon chief executive officer Jeff Bezos, 46, bought Zappos.com Inc. last year for $1.2 billion to expand sales of shoes and clothing. The purchase also removes a competitor for Seattle-based Amazon, which began selling diapers in mid-2006, a year after Diapers.com debuted.