The Cisalpino railway company has taken its problematic tilting train fleet out of service, six months before it was due to be upgraded.
Rail passengers between Basel and Milan will instead travel on conventional trains leased from Swiss Railways and the Italian state rail company, Trenitalia, the firm announced on Thursday.
Travellers will also have to change trains in Domodossola, the first station inside Italy, instead of the usual direct service. However, Cisalpino says this will only add a few minutes to the total journey.
It has promised compensation to anyone delayed for more than 45 minutes.
The company says it has taken the step in order to speed up maintenance work on the trains, which is conducted in Italy. It hopes to restore the through service in a few weeks.
The tilting train has run into problems ever since coming into service 12 years ago. Its fittings are often unreliable, and it frequently runs late.
An improved generation of the train was originally due to be delivered in May 2007; they are now scheduled to come into service in June 2009.
Cisalpino is a joint venture of the Swiss and Italian state railway companies.