DHL Worldwide Express, a delivery service owned by Deutsche Post AG of Germany, has agreed to acquire the ground delivery business of Seattle-based rival Airborne Express for about $1 billion. The deal creates a stronger competitor to United Parcel Service and Federal Express in the U.S. Although recognized as the largest foreign overnight carrier, DHL has been a distant third to UPS and FedEx in the U.S. because it previously lacked a ground delivery network.