ZURICH (Reuters) - Former intelligence contractor Edward Snowden could be granted safe passage in Switzerland if he helped a potential criminal inquiry into U.S. spying there, the Swiss public prosecutor's office said on Monday.

He would probably not be extradited to the United States if Washington asked, but it was also unlikely that he would be granted political asylum, according to a document laying out Switzerland's legal options if Snowden were to visit.

The prosecutor's office, which provided the document to Reuters, stressed the issue was "purely hypothetical" because Snowden had not been invited to come from his current refuge in Russia. It had no further comment.

The document was leaked last week and prompted a lively debate in the Swiss media.

Some German politicians have suggested inviting Snowden to Germany to testify about National Security Agency spying there, but Berlin has ruled that out to avoid a clash with Washington over extraditing him to the United States.

Michael McCaul, Republican head of the U.S. House of Representatives Committee on Homeland Security, reacted to the Swiss debate by telling the U.S.-based Foreign Policy magazine that Snowden should not be allowed to "trade our intelligence community's sources and methods for safe haven in other countries".

GENEVA CIA ACTIVITIES

According to the three-page Swiss document, "Edward Snowden could be assured of free movement by the federal prosecutor if he cooperated with a criminal investigation" into U.S. spy activities he says he learned about while working in Geneva.

Switzerland would not comply with a U.S. extradition request if he is accused of treason or divulging state secrets because such charges would have a "political character" under Swiss law, the document said.

The guarantee for Snowden's free passage in Switzerland could be trumped by "higher state obligations" such as a treaty, the document said, adding this required more study.

Marcel Bosonnet, Snowden's lawyer in Switzerland, did not comment on the document.

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The prosecutors said Snowden was not likely to be granted asylum in Switzerland because he has already been given a three-year residency in Russia last month.

The decision on whether to grant Snowden asylum in Switzerland ultimately lies with the government and with justice officials.

Snowden worked as a computer technician for the Central Intelligence Agency in the U.S. mission to the United Nations in Geneva between 2007 and 2009.

He has told London's Guardian newspaper he had a "formative" experience in the Swiss city when the CIA deliberately got a Swiss banker drunk and encouraged him to drive home.

When he was arrested, a CIA operative offered to intervene and later recruited the banker, Snowden has claimed. Some Swiss officials have questioned if the incident ever happened.

(Reporting by Katharina Bart in Zurich and Mark Hosenball in London; Editing by Tom Miles and Tom Heneghan)