The SFr 1.86bn ($US 2.06bn) contract was signed in May 2010 and is SBB's largest-ever rolling stock procurement, as well as being the first ever order for tilting double-deck emus. Deliveries were due to commence in December 2013 with the final sets scheduled to enter service at the end of 2019.

However, SBB has now confirmed that the first trains will not be delivered before December 2015.

In a statement, SBB said: "The contract between SBB and Bombardier includes penalties for failure to deliver. In view of the size of the contract and the associated penalties, a lengthy dispute is anticipated, for which SBB has prepared accordingly. SBB and Bombardier will do everything possible to make the trains available for use as soon as possible."

Meanwhile, SBB has announced that it will reveal the winning bidder in May for a contract to supply 29 new 250km/h multi-system trains for international services between Germany, Switzerland and Italy via the Gotthard Base Tunnel. The trains are due to enter service in 2017.