In a little-noticed tweet Sunday, a U.S. State Department spokeswoman delivered an unusually blunt criticism of South Korea's decision to pull out of an intelligence-sharing pact with Japan, saying that the move endangers American troops.

"We are deeply disappointed and concerned that the ROK's government terminated the General Security of Military Information Agreement #GSOMIA," U.S. State Department spokeswoman Morgan Ortagus wrote. "This will make defending #Korea more complicated and increase risk to U.S. forces."

The Trump administration has already voiced its disappointment over South Korean President Moon Jae-in's Thursday announcement that Seoul would stop participating in the 2016 agreement with Japan, though it had not noted the danger doing so put U.S. troops in.