U.S. Secretary of State John Kerry and other foreign ministers from the six-power group negotiating a final nuclear agreement with Iran will join the talks in Vienna this weekend, officials confirmed late Thursday. Michael Mann, the spokesman for European Union foreign policy chief Catherine Ashton, chairwoman of the six-power group, said on Twitter that she had invited foreign ministers “who are available to come to Vienna on Sunday to take stock of where we are in talks.” A Western diplomat said some of the foreign ministers will likely start arriving on Saturday as Iran and the six powers try to forge a comprehensive nuclear deal by a July 20 deadline. The diplomat said it isn’t yet clear whether all the ministers will be able to come in person. However, State Department deputy spokeswoman Marie Harf confirmed that Mr. Kerry would join the negotiations, which will include Iranian Foreign Minister […]