China is closer to joining the major league of reserve currencies with a deal possible later this year to include the yuan in the International Monetary Fund’s unit of account, international finance officials say. U.S. Treasury Secretary Jack Lew said after a visit to Beijing this week the yuan was not yet ready to join the virtual currency that defines the value of the IMF’s reserves, used for lending to countries in financial difficulty. Beijing has made strides this year in introducing the infrastructure needed to float it freely on global capital markets.