“These files conclusively prove that Iran is brazenly lying when it said it never had a nuclear weapons program,” Mr. Netanyahu said, pointing to copies of what he said were 55,000 printed pages and 183 compact discs.
He said Israel had passed the information on to the United States, which “can vouch for its authenticity.”
Mr. Netanyahu said that Iran had intensified its efforts to hide evidence of its weapons program after signing the nuclear deal in 2015, and in 2017 moved its records to a secret location in Tehran that looked like “a dilapidated warehouse.”
“Few Iranians knew where it was, very few,” Mr. Netanyahu said proudly. “And also a few Israelis.”
The senior Israeli official, who spoke on the condition of anonymity to discuss a secret mission, said that Israel’s Mossad intelligence service discovered the warehouse in February 2016, and had the building under surveillance since then.
Mossad operatives broke into the building one night last January, removed the original documents and smuggled them back to Israel the same night, the official said.
Mr. Trump was informed of the operation by the Mossad chief, Yossi Cohen, on a visit to Washington in January, the official said. The official attributed the delay in making the material public to the time it took to analyze the documents, the vast majority of which were in Persian.
But the Iranian program to design and build nuclear weapons was hardly a secret; its existence was the reason that the United States, under President George W. Bush and then President Barack Obama, moved to block it. Both presidents said publicly that Iran had a bomb project underway, and the United States mounted, with Israel, a vast covert program to undermine the Iranian effort with one of the world’s most sophisticated cyberattacks.