President Obama is pressing United Nations nuclear inspectors to release classified intelligence information showing that Iran is designing and experimenting with nuclear weapons technology. The president’s push is part of a larger American effort to further isolate and increase pressure on Iran after accusing it of a plot to assassinate Saudi Arabia’s ambassador to the United States…

The decision to press the International Atomic Energy Agency was brewing even before the plot against the Saudi ambassador was discovered, but that discovery prompted the White House to pursue a full-court, public press of the agency to release the sensitive intelligence.

Officials familiar with the evidence say it creates extraordinarily uncomfortable questions for the Iranians to answer, but does not definitively point to the construction of a weapon. Instead, it details work on individual technologies essential for designing and detonating a nuclear device, including how to turn uranium into bomb fuel, how to cast conventional explosives in a shape that can set off a nuclear blast, and how to make detonators, generate neutrons to spur a chain reaction, measure detonation waves and make nose cones for missiles…

“They sought to hide their enrichment activity for years, and their covert facility at Qum, which the president revealed in 2009,” a top adviser to Mr. Obama, who spoke on the condition of anonymity because of the delicacy of the topic, said Friday. “They continue to enrich at 20 percent, and the rationale for doing so is demonstrably false.”