South Korea's chief nuclear envoy headed home on Wednesday after a three-day trip to the United States for talks with his American and Japanese counterparts. 

Lee Do-hoon, special representative for Korean Peninsula peace and security affairs, had bilateral and trilateral meetings with U.S. envoy Stephen Biegun and Japanese envoy Shigeki Takizaki in Washington on Tuesday.

Before departing for Seoul at Dulles International Airport, Lee told reporters that the three sides agreed to continue joint efforts to make progress on the North's denuclearization.

Lee, however, did not elaborate further on the discussions, saying North Korea could use his remarks as an excuse. He added his counterparts also agreed not to disclose details of the discussions. 

Lee's U.S. visit came after American nuclear envoy Stephen Biegun and his North Korean counterpart Kim Myong-gil resumed working-level nuclear negotiations in Sweden last week but broke off talks hours later without an agreement.