South West Norfolk MP Elizabeth Truss has received a letter from transport minister Mike Penning, saying work will start between January and March.
She said: “This is very good news and illustrates the government’s commitment to infrastructure projects which promote growth and employment.
“The time frame for the construction has been brought forward and some preparatory work has already commenced around the Elveden Estate.
“I know residents and businesses from across the region will be very pleased by this announcement.”
The scheme was awarded to Birse in November 2009 but was delayed by spending cuts.
Work will involve dualing the last single carriageway section of the A11, which stretches nine miles (15 km) between Fiveways Roundabout at Barton Mills near Mildenhall, and the roundabout at the southern end of Thetford Bypass.
The scheme will also include a bypass to take traffic away from the village of Elveden, which has Conservation Area status.