LONDON (AP) — The British government says there could be lines of 7,000 trucks at the English Channel and two-day waits to get into France immediately after the U.K. makes its economic break from the European Union at the end of the year.

Michael Gove, the minister in charge of Brexit preparations, described that as a reasonable worst-case scenario in a letter to logistics firms. He’s due to give more details to Parliament on Wednesday.

The government letter says that between 30% and 50% of trucks wanting to cross the Channel may not be ready for new paperwork and regulations that will come into effect on Jan. 1.

“This could lead to maximum queues of 7,000 port-bound trucks in Kent and associated maximum delays of up to two days,” the document said.

The U.K. withdrew from the EU’s political institutions on Jan. 31 but remains in a tariff-free transition period until the end of the year while negotiators try to work out a future trade relationship.

Even with a deal, Britain will be leaving the bloc’s single market and customs union, meaning some new checks and trade barriers. Without a deal there will be much greater disruption, with the U.K. and the EU having to slap tariffs on each others’ goods.

The two sides say a deal must be struck by October so it can be approved and ratified before Jan. 1. But negotiators remain at loggerheads on key issues, especially European fishing boats’ access to U.K. waters and competition rules for businesses.

Chief EU negotiator Michel Barnier is due to hold talks with his British counterpart David Frost in London Wednesday ahead of a ninth formal round of negotiations next week.

The climate for the talks has been further chilled by British Prime Minister Boris Johnson’s introduction of a bill that would give the U.K. the right to override parts of the legally binding withdrawal agreement it struck with the bloc less than a year ago.

That has infuriated the EU, which has threatened legal action if Britain does not reverse course by the end of September. Johnson shows no signs of dropping the bill, which is currently making its way through Parliament.

The legislation has also caused an uproar in Britain. Five former prime ministers have criticized Johnson’s willingness to break international law, and the government’s top legal civil servant and most senior law officer for Scotland have both resigned.