WASHINGTON — Iran is likely to respond to new attacks from Israel or additional Western sanctions by edging ever closer to crossing the nuclear threshold, according to a just-released U.S. intelligence assessment. The unclassified report, issued Thursday by the Office of the Director of National Intelligence, finds that while Tehran is not currently poised to build a nuclear weapon, it is undertaking activities “that better position it to produce one, if it so chooses.” The report states that since July, Iran has continued to increase its stockpiles of 20% and 60% enriched uranium while also manufacturing and operating a growing