WRAPUP 7-Kerry extends Iran talks, French foreign minister returns

* French foreign minister returns to talks * Russia, Iran say agreement reached on key issues * Western negotiators said agreement still elusive * U.S. says it will exit talks before June 30 if no deal (Adds Germany's Steinmeier, White House, Zarif, French return) By Louis Charbonneau, John Irish and Parisa Hafezi LAUSANNE, Switzerland, April 1 (Reuters) - U.S. Secretary of State John Kerry and his German and French counterparts extended marathon talks in Switzerland on Wednesday for a second da