Major powers and Iran negotiated into the early hours of Thursday on Tehran’s nuclear program two days past their deadline, with diplomats saying prospects for a preliminary agreement were finely balanced between success and collapse. The negotiations, aimed at blocking Iran’s capacity to build a nuclear bomb in exchange for lifting sanctions, have become bogged down over crucial details of the accord, even as the broad outlines of an agreement have been reached. After negotiators passed an original self-imposed deadline of midnight on Tuesday, they remained locked in talks through to the early hours of Thursday in the Swiss city of Lausanne. “It is going to be long,” said a senior diplomat. “That was truly an all-nighter,” Marie Harf, spokeswoman for U.S. Secretary of State John Kerry, said on her Twitter account, noting negotiators broke up at 6.00 a.m local time (0400 GMT) and would […]