US Secretary of State John Kerry said Tuesday it would soon become clear if Iran is serious about ending suspicions over its nuclear ambitions, as World powers appeared to inch towards a historic deal with Tehran. World powers grouped under the so-called P5+1 "had made inroads" since reaching an interim deal with Iran in **vember 2013 on reining in its suspect nuclear program, Kerry said. "And we expect to k**w soon whether or **t Iran is willing to put together an acceptable, verifiable plan," he said, adding bluntly: "I don't k**w yet." As the talks gather pace with the Iranian and US teams due to meet again in Switzerland on Monday, possibly with Kerry, EU foreign policy chief Federica Mogherini insisted a deal was "at hand." "We can**t miss this opportunity," Mogherini told Chatham House, a London think tank. Kerry again stressed that US policy was that Tehran would **t acquire a nuclear ******.