A group representing European car makers is urging Brexit negotiators to urgently address issues affecting the industry and prevent "potentially disastrous implications" for its supply chain.
The European Automobile Manufacturers' Association (ACEA) said it is concerned about whether cars approved by UK authorities can still be sold in the EU after Brexit, and vice versa.
It called for both sides to recognise each other's vehicle approvals.
It also said that any new customs checks "would add cost, cause delays and threaten productivity".
With the UK due to leave the European Union at the end of March 2019, its post-Brexit relationship with the EU has yet to be worked out.
EU leaders are set to approve an outline for future negotiations with Britain at a summit later this week.