An archaeological find has delayed the decision on whether to build a £2.4bn road tunnel near Stonehenge.
Transport Secretary Grant Shapps has pushed back the announcement to November to allow for "further consultation".
The proposed tunnel would remove the sight and sound of traffic from the frequently congested A303 route, Highways England has said.
Campaigners have argued the scheme would damage the World Heritage site.
Salisbury MP John Glen said the announcement would be "unwelcome news" to local residents, particularly those in Shrewton, which is close to the landmark.
He added: "I'm still optimistic that we will get to the final green light in November. I regret the delay but we've got to do these things properly."
The Planning Inspectorate handed its recommendations to Mr Shapps in January, and he was due to make his decision on Friday.
Last month it emerged that a team of archaeologists had discovered a ring of at least 20 large shafts a short distance from Stonehenge.
It is thought they form the largest prehistoric monument ever discovered in Britain, and experts believe they may have served as a boundary to a sacred area.
Announcing the delay, Transport Minister Andrew Stephenson said the decision to add the four-month extension was "without prejudice to the decision on whether to give development consent."
Earlier this year the two-mile (3.2km) tunnel was given the green light by chancellor Rishi Sunak.
Officially known as the A303 Amesbury to Berwick Down Improvement, the plan includes a flyover at Countess Roundabout in Amesbury, alongside the Blick Mead settlement, and a bypass for Winterbourne Stoke.
More than 54,000 people have signed a petition started by the Stonehenge Alliance, which opposes the plans.
It said if the tunnel had to go ahead it should be a deep-bored tunnel of at least 2.8 miles (4.5km) long.
"Anything shorter would cause irreparable damage to this landscape, in breach of the World Heritage Convention," the group said.
Derek Parody, Highways England project director for the A303 Stonehenge scheme, said: "We are confident that the proposed scheme presents the best solution for tackling the longstanding bottleneck on this section of the A303, returning the Stonehenge landscape to something like its original setting and helping to boost the south-west economy."