Rising costs has been blamed for the decision to put back the dualling of the A9 between Inverness and Perth back 10 years to 2035.
Transport secretary of the devolved government Mairi McAllan explained that the cost from an original estimate of £3bn had now risen to £3.7bn.
Finishing the project by the original date of 2025 is now said to be ‘unachievable’.
Mairi McAllan updated Parliament on the delivery plan whereby almost 50% of the road is expected to be dualled by the end of 2030, rising to 85% by the end of 2033, with the final section expected to open by the end of 2035.
Since 2013, two parts of the A9 totalling 11 miles have been upgraded from single carriageway to dual-carriageway, and there is more than 75 miles still to be done.