Construction will begin this summer on an expansion of the passenger and baggage areas of Dulles International Airport, the U.S. Department of Transportation said yesterday.

The department said it has awarded a $6,649 million contract to Frank Briscoe Co. Inc. of East Orange, N.J., for the work, which will not alter the basic configuration of the architecturally acclaimed terminal building.

The work, which will take two years, will be done on the airfield side of the terminal, designed by the late Eero Saarinen. It will add about 75 feet to the width of the terminal at ground level, where baggage is collected, and 50 feet on the concourse, or passenger, level. The addition was proposed in 1972, and approved by various reviewing bodies.

The expansion was not part of Saarinen's design, which did foresee the eventual lengthwise expansion of the cantilevered, glass-enclosed terminal.

However, DOT spokesman Dave Hess said the baggage and passenger areas have become more congested than anticipated because of the use of widebodied planes and the need for security-clearance areas.

The terminal recently was declared eligible by the Interior Department for inclusion in the National Register of Historic Places, and Secretary of Transportation Brocks Adams is expected to submit the nomination soon.