The United States is ready to contribute $20 billion as its portion of a $50 billion loan package to Ukraine that it is planning with other Group of Seven countries, Treasury Secretary Janet Yellen said Tuesday. At a press conference in Washington ahead of this year’s meetings of the International Monetary Fund and the World Bank, Yellen said the G7 countries, including Britain, Germany and Japan, are close to finalizing the package, which uses interest earned on frozen Russian sovereign assets, mostly in Europe. The leaders of the group agreed in principle on such financial assistance to Ukra…