The US Supreme Court declined to intervene Monday in the case of a New York Times reporter involving the protection of sources and the CIA.
The top panel rejected an appeal by journalist James Risen, who has been summoned to testify in the trial of former Central Intelligence Agency official Jeffrey Sterling.
Sterling stands accused of leaking confidential information about a secret Iran operation.
In his book "State of War," published in 2006, Risen describes an aborted CIA effort to send a former Russian scientist to Iran to transmit false information in an attempt to undermine the country's controversial nuclear program.
The Supreme Court did not comment on its decision, which upholds an order to testify issued to Risen by a federal appeals court.
Risen, who faces jail time if he refuses to reveal his sources, did not immediately respond to an AFP request for comment.
The case is being seen as a test of the freedom of the press in investigating government abuses.