In the 1970s the US commercial airframe manufacturers were following closely the progress of the Airbus A300's development. In the spring of 1976, Boeing proposed a joint airliner based on a Boeing wing and an A300 fuselage designated the BB10. Talks continued for sometime despite mutual suspicions in Seattle and Toulouse with Airbus eventually deciding to abandon the BB10 project. Boeing then approached British Aerospace about a risk-sharing partnership in the 757 program, but to no avail.
Source: Airbus A300 (Airliner Color History) by GUnther Endres. MBI Publishing, 1999, p56.