The U.S. State Department says it will continue to enforce sanctions on North Korea.

Department spokesman Philip Crowley said in a daily briefing Thursday in Washington that the U.S. will continue to enforce U.N. Security Council Resolution 1874 to prevent nuclear proliferation.

Regarding the ongoing Key Resolve joint military drill with South Korea, Crowley said that the military exercises have been done in the past and that they should not be a surprise to North Korea.

The North's foreign ministry said in a statement earlier in the week in reference to the Key Resolve and Foal Eagle exercises that as long as the U.S. military threat and provocations continue, the North will continue to strengthen its nuclear deterrent.