YUMEN — The scale and speed of construction at possible missile silo fields in China suggests its government is putting significant resources into developing its nuclear capabilities, with a new Federation of American Scientists report increasing an estimate of the total number of new silos being built from the 229 described in a previous report to 300. The new report is careful to state that it is not certain what is in the silos, but says there is “increased confidence” that they are related to the People’s Liberation Army Rocket Force’s modernization program and, based on commercially available satellite images, it describes significant progress on construction since the earlier report in July. It also describes how China appears to be experimenting with different types of shelters at the three silo field sites near Yumen, Hami and Ordos in north-central China, before concluding that although China is currently still far behind the U.S. and Russia’s total nuclear arsenal, the new silos could see China’s total intercontinental ballistic missile force exceed that of either Russia and the United States in the foreseeable future.