MONTREUX, Switzerland (Reuters) - U.S. Secretary of State John Kerry quietly cautioned Israel not to undercut nuclear negotiations with Iran that resumed on Monday as Israeli Prime Minister Benjamin Netanyahu prepared to make the case in Washington against the diplomacy. Kerry and Iranian Foreign Minister Mohammad Javad Zarif met for about 90 minutes on the first of what could be three days of talks in the Swiss lakeside town of Montreux on curbing Iran's nuclear program in exchange for relief from economic sanctions.