(Reuters) – Leading U.S. senators expressed alarm on Thursday at the scale and speed of China’s land reclamation in the South China Sea and said a formal U.S. strategy was needed to slow or stop the work.

In a letter to U.S. Secretary of State John Kerry and U.S. Defense Secretary Ash Carter, Republican Senators John McCain and Bob Corker and Democrats Jack Reed and Bob Menendez said that without a comprehensive strategy “long-standing interests of the United States, as well as our allies and partners, stand at considerable risk.”

They said China’s land reclamation and construction in the South China Sea’s Spratly archipelago gave it the potential to expand its military reach and was “a direct challenge, not only to the interests of the United States and the region, but to the entire international community.”

The letter said Gaven Reef had grown about 28 acres (114,000 square meters) in the past year and previously submerged Johnson Reef was now a 25-acre (100,000-square-meter) “island.” Fiery Cross reef increased in size more than 11-fold since August.

Read more: http://www.reuters.com/article/2015/03/19/us-usa-china-southchinasea-idUSKBN0MF2SQ20150319