U.S. Treasury Secretary Janet Yellen kicked off a four-day visit to Beijing on Friday by calling for market reforms in the world's second-largest economy and warning that the United States and its allies will fight back against what she called China's "unfair economic practices." In a meeting with Chinese Premier Li Qiang, Yellen said that the U.S. is seeking healthy competition with China based on fair rules that benefit both countries, not a "winner-take-all" approach.