Ashley Tellis, 64, who held senior positions under former president George W. Bush and remained an unpaid advisor to the State Department, was arrested Saturday and faces up to 10 years in prison.

"Ashley J. Tellis is a widely respected scholar and senior policy advisor," his lawyers, Deborah Curtis and John Nassikas, said in a statement.

"We will be vigorously contesting the allegations brought against him, specifically any insinuation of his operating on behalf of a foreign adversary," they said.

A criminal affidavit made public Tuesday said that Tellis went into the State Department late on September 25 and appeared to print from a secret document on US Air Force techniques.

It alleged that Tellis met repeatedly with Chinese officials at a restaurant in the Washington suburb of Fairfax, Virginia, and that at one dinner he appeared to leave a manila envelope.

The charges announced by the Justice Department relate to improper handling of documents rather than the meetings, with an FBI special agent saying a search found more than 1,000 pages of top-secret or secret documents in his house.

Tellis has been a senior fellow at the Carnegie Endowment for International Peace, a leading Washington think tank, which said Wednesday that he has been put on administrative leave.

Tellis, a naturalized American originally from India, helped negotiate the Bush administration's civil nuclear cooperation deal with India, a landmark step to closer relations between the world's two largest democracies.

But Tellis in recent years has emerged as a leading contrarian in Washington about India, saying that New Delhi's interests were not aligned on a host of issues including Ukraine.