DUBAI (Reuters) -Iran's Supreme Leader Ayatollah Ali Khamenei said U.S. demands that Tehran stop enriching uranium are "excessive and outrageous", state media reported, voicing doubts whether talks on a new nuclear deal will succeed. "A date has been suggested but we have not yet accepted it," Foreign Minister Abbas Araqchi told state media on Tuesday when asked about a fifth round of talks, which an Iranian official said on Monday might be held this weekend in Rome. The talks on a new nuclear deal appear on shaky ground as both Iran and the U.S. have clashed over the issue of uranium enrichment.