The opening of the Lötschberg-Simplon tunnel through the Alps has been delayed by six months. Construction suffered setbacks on the Italian side, partly because of extreme weather conditions last autumn.
The tunnel was scheduled to be finished by January 1, but is now not expected to be completed before June 10.
Max Friedli, director of Switzerland's Transport ministry, told the Swiss Broadcasting Corporation that he would send specialists to Italy to evaluate the situation.
Italy's railway company blamed bad weather last autumn for the delay. It said some of the construction sites had been damaged, while others had to be closed.
But Friedli said that the Italians had already been running behind schedule before last autumn's storms, and had asked for the deadline to be postponed until March.
Friedli added that Switzerland's influence on the Italian construction effort was limited because Italy was financing it.
The Lötschberg-Simplon tunnel is being built to transfer 40-tonne trucks from road to rail.
swissinfo with agencies