The U.S. ambassador to Switzerland says hundreds of Swiss dual citizens have given up their American passports in what he calls a “big phenomenon” now in the country.

Donald Beyer told the business paper the Handelszeitung that stricter enforcement of U.S. laws make having a US passport less attractive.

He said the relationship with Switzerland only has one problem: American justice officials trying to pursue tax evaders without infringing on Swiss laws.

The paper asked Beyer why the American relationship was so much better with Liechtenstein, to which he replied that the principality made a decision to break from black or gray lists, and adopted a “clean money strategy” very early.

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