Conventional Prompt Global Strike and Long-Range Ballistic Missiles: Background and Issues [Updated August 14, 2019] [open pdf - 1MB]
From the Document: "Conventional prompt global strike (CPGS) weapons would allow the United States to strike targets anywhere on Earth in as little as an hour. This capability may bolster U.S. efforts to deter and defeat adversaries by allowing the United States to attack high-value targets or 'fleeting targets' at the start of or during a conflict. Congress has generally supported the PGS [prompt global strike] mission, but restricted funding for several years. Recently, efforts to develop a long-range prompt strike capability, along with other efforts to develop extremely fast hypersonic weapons, have garnered increased support."
CRS Report for Congress, R41464
Congressional Research Service: https://crsreports.congress.gov/