Kerry, Zarif see hard work ahead as nuclear talks begin

By Arshad Mohammed and Parisa Hafezi VIENNA (Reuters) - Senior U.S. and Iranian officials said much hard work still needs to be done to bridge significant differences on an agreement to curb Iran's nuclear programme. With a deadline approaching on Tuesday, each side sought to place the onus on the other to finalise a deal under which Iran would cut back its nuclear programme in exchange for relief from economic sanctions. "If the other side...takes positive steps and does not make exce