A planning row could hit the capacity of a 190-mile pipeline being built across south Wales, the National Grid has warned.
Construction of the liquefied natural gas (LNG) pipe from Milford Haven to Gloucestershire has already been disrupted by environmental campaigners.
But now a delay in planning permission for a pipe terminus at Cilfrew, near Neath, is causing further problems.
National Grid said it was still assessing the full impact on supply.
The latest setback comes after a series of protests, including a demonstration last November when work in the Swansea Valley was halted by protestors who climbed inside the pipe.
However, phase one of the pipeline from Milford Haven to Aberdulais, is over 95% complete, and phase two from Felindre to Gloucestershire is said to be "well under way".
Eventually, the 190-mile pipeline will carry around 20% of gas needed to meet the UK's energy supply.
But the National Grid said work at Cilfrew had been suspended until planning permission is given, and the pipe would not work at full capacity until work there was complete.
Initially, the scheme to build the terminus was approved by the planning committee of Neath Port Talbot Council.
But some local people were unhappy that four councillors who had attended an earlier protest meeting against the plans had been advised not to vote by council officials.
The residents sought a judicial review, and last month a High Court judge struck down the planning committee's decision as "unlawful" and ordered the vote be taken again.
The council is unlikely to vote on the planning permission again until at least 15 May, according to the National Grid.
A spokesman for the company said it would only be possible to make an accurate estimate of what capacity will be available for shippers importing gas to Milford Haven when the terminals open next winter.
Meanwhile, National Grid said work on the pipeline was continuing and it would progress with other parts of the project as quickly as it could.