It is understood the county council is negotiating with land owners near the new Carmarthen west link road.
Persimmon Homes said the council "had to cease work on the road" while discussions continued.
Carmarthenshire council has refused to confirm why the work has stopped on the road, which is west of Carmarthen.
BBC Wales understands Alun Griffiths (Contractors) Ltd, has not been on site at the junction near the A40 at Travellers Rest for several months.
The council maintains the work will be completed by 2018.
Executive board member for environment Hazel Evans said: "Work has reached staged completion on the road in line with the programme. We are completing works on car park areas currently.
"We have licence to work on the route whilst negotiations are finalised on a part of the land."
The new road will improve access to key employment sites at St David's Park, the University of Wales Trinity St David and Coleg Sir Gar and serve the new S4C headquarters Yr Egin.
The Welsh Government contributed Â£1.3m towards the cost of the road, with further support from the University of Wales, Trinity St David.
A new junction at Jobswell Road was completed in October as part of the project and was described by the council as the "first phase of the Â£5m Carmarthen west link road" but no mention of phasing the construction was made in the original planning document.
A spokesman for Persimmon Homes said it remained "committed to its significant development in Carmarthen west and to meeting its obligations for infrastructure investment".
Work has stalled on a Carmarthenshire link road which will connect 1,000 homes and S4C's new headquarters, BBC Wales has learned.