Critics of the prosecution of Steven Rosen and Keith Weissman of the American Israel Public Afffairs Committee had accused the federal government of trying to criminalize the sort of back-channel discussions between government officials, lobbyists and reporters that are commonplace in the nation's capital. AIPAC is an influential pro-Israel lobbying group.

Acting U.S. Attorney Dana Boente said the government moved to dismiss the charges in the drawn-out case after concluding that pretrial rulings would make it too difficult for the government to prove its case.

U.S. District Judge T.S. Ellis III had made several legal rulings that prosecutors worried would make it almost impossible to obtain a guilty verdict. Among them was a requirement that the government would have to prove that Rosen and Weissman intended to harm the United States by trading in sensitive national defense information.

The trial had been scheduled to start June 2 in a case that has dragged on for four years.

Rosen and Weissman had not been charged with actual espionage, although the charges did fall under provisions of the 1917 Espionage Act, a rarely used World War I-era law that had never before been applied to lobbyists.

A former Defense Department official, Lawrence A. Franklin, previously pleaded guilty to providing Rosen and Weissman classified defense information and was sentenced to more than 12 years in prison.