Eurostar passenger train services linking Britain to continental Europe will be suspended for a third day Monday, the company said, after a series of trains broke down due to the freezing weather.
The company gave no guarantees that the high-speed services linking London with Paris and Brussels would be back to normal on Tuesday, but said it was modifying trains to prevent them breaking down again.
"Eurostar will not be operating services on Monday," the company said in a statement on its website.
"We sincerely regret having to take this decision and we understand how frustrated and disappointed travellers will be, particularly those who have been waiting to travel for the last two days.
"We strongly advise passengers whose travel is non-essential to change their booking to a later date or claim a refund on their tickets. We have also announced our compensation policy for inconvenienced travellers.
"We will provide a further update regarding Tuesday's services by 1800 GMT on Monday."
Eurostar's commercial director Nick Mercer said test trains had been running Sunday with engineers trying to work out what was making them break down in the cold weather.
They had made modifications to the trains, which will be tested Monday, he said.
"The test trains did run satisfactorily. The engineers believe they've found the cause," he told BBC television.
The weather conditions in northern France "caused snow to be ingested into the trains in a way that's never happened before... This is a fault we had never seen before," he said.
"We're carrying our the modifications and I sincerely hope when we test those modifications in live service on these test trains, they will work satisfactorily and we'll be able to resume service.
"We will be running test trains with the modifications on board to 100 percent check that they work.
"Our priority is to get trains back into service as soon as possible."