The main targets are US industrial and technical secrets, the weekly said, quoting classified briefings on legislation that would make it easier for Israeli citizens to get visas to enter America.

Newsweek said a congressional staffer familiar with a briefing last January called the testimony "very sobering ... alarming ... even terrifying", and quoted another as saying the behavior was "damaging."

"No other country close to the United States continues to cross the line on espionage like the Israelis do," said a former congressional staffer who attended another classified briefing in late 2013, according to Newsweek.

It said that briefing was one of several in recent months given by the Department of Homeland Security, the State Department, the FBI and the National Counterintelligence Directorate.