Defense Secretary Jim Mattis warned North Korea's ramped-up efforts to develop a missile capable of carrying nuclear weapons that pose a danger to the U.S. and its allies represents a "clear and present danger."

"North Korea's continued pursuit of nuclear weapons and the means to deliver them is not new, but the regime has increased the pace and scope of its efforts," Mattis said at the international security conference in Singapore on Saturday.

"As a matter of national security, the United States regards the threat from North Korea as a clear and present danger," the defense secretary said.

China blocked new sanctions on North Korea that the U.S. pushed through to the United Nations Security Council. However, the Council did agree to add 15 new North Koreans linked to nuclear weapons to a U.N. sanctions blacklist.

Mattis said Chinese commitment to working with the U.S. to rid North Korea of nuclear weapons is encouraging, according to the Associated Press. He also said its only a matter of time until China, an ally of North Korea, sees the danger in North Korea's having nuclear weapons.