Switzerland has asked Germany to explain why it has imposed stringent border checks.
Border officials believe this recent move may have been designed to put pressure on Bern to wrap up a series of stalled bilateral treaties with the European Union.
"We're surprised by these measures, their timing and the reasoning behind them," says Walter Pavel of the Federal Customs Office in Bern. "The German border guards have been very relaxed in their controls until now," he adds.
The Swiss finance minister, Hans-Rudolf Merz, will raise the issue with his German counterpart, Hans Eichel.
Tougher checks on people and vehicles entering Germany from Switzerland are causing daily traffic jams several kilometres long on the Swiss side of the border.
One of the worst affected crossing points is in Basel.
Thorsten Neuwirth of the Southern German Customs Office in Munich stated that the checks had been intensified to comply with the Schengen...