By Sarah N. Lynch WASHINGTON (Reuters) - U.S. Treasury Secretary Jack Lew has urged top European finance ministers and the International Monetary Fund to continue working together toward a "sustainable solution" to reforms in Greece and its recovery within the euro zone. Lew spoke by phone with several top officials on Saturday, including the finance ministers of Germany and France and IMF Managing Director Christine Lagarde, according to a readout of the call provided by the Treasury Department on Sunday.