South Korea's top nuclear envoy visited the United States on Sunday amid heightened tensions on the Korean Peninsula over the recent death of a South Korean official in North Korean waters. 

Arriving at Dulles International Airport in Washington, Lee Do-hoon, special representative for Korean Peninsula peace and security affairs, told reporters that he will discuss with the U.S. how to cooperate on the incident.

During the four-day trip, Lee will meet with U.S. Deputy Secretary of State Stephen Biegun, who doubles as the point man for North Korea.

Lee said the two sides will also discuss a formal declaration to end the Korean War as he is visiting the U.S. to discuss all pending issues during the trip. 

He added that Washington had also examined the issue many times with interest, and South Korea and the U.S. could seek a consensus if they talk face to face. 

South Korean President Moon Jae-in recently called for global support for a formal declaration to end the Korean War in his address to the U.N. General Assembly.