It is normal to sell US Treasury bonds. If you don't sell US Treasury bonds and have no cash, you can't meet the net demand for foreign exchange purchase caused by the deficit in foreign exchange settlement and sale.

Although the sale of US Treasury bonds will affect the stock of China's foreign exchange reserves, it should also meet the normal demand of enterprises and individuals for foreign exchange purchase. The purpose of accumulating foreign reserves was to cope with the greater pressure of capital outflow in the future. The purpose of foreign exchange reserves is to meet the needs of foreign investment and trade, including people's normal asset allocation needs.