The road job was due to start in January but was delayed as legal agreements were thrashed out over land.
The 2.3 km long single carriageway forms part of a wider scheme, which will eventually include a new secondary school and around 500 new homes in the Moreton Hall area of the town.
It will also enable the expansion of Suffolk Business Park and is expected to create up to 15,000 jobs over the next 25 years.
A 560m length of existing road will require reconstruction along with five new roundabouts and alterations to the slip roads that connect with the A14.
