By Parisa Hafezi and Francois Murphy VIENNA (Reuters) -Russia’s demand for written U.S. guarantees that sanctions on Moscow would not harm Russian cooperation with Iran is “not constructive” for talks between Tehran and global powers to revive a 2015 nuclear deal, a senior Iranian official said on Saturday. The announcement by Russia, which could torpedo months of indirect talks between Tehran and Washington in Vienna, came shortly after Tehran said it had agreed a roadmap with the U.N. nuclear watchdog to resolve outstanding issues that could help secure the nuclear pact. “Russians had put th…