Transport campaigners have said they believe the Treasury may announce additional public funding for the widening of the A14 in the coming days.
A spokesperson for the Campaign for Better Transport said that difficulties in raising private investment may prompt the government to announce the extra support, although details of routing and cost are not expected until the Autumn.
The A14, which links the Port of Felixstowe to the British road network, has been heavily congested for years. The government has sponsored a series of studies into the possibility of charging a toll to pay for the work.
It is one of a number of large infrastructure schemes that may receive financial support when the Chancellor gives his spending review on Wednesday.