A United States delegation reportedly held a fourth round of summit preparation talks with North Korean officials on Sunday in the truce village of Panmunjeom.

The delegation, led by U.S. Ambassador to the Philippines Sung Kim, is said to have held talks with the North's Vice Foreign Minister Choe Son-hui and other North Korean officials for over three hours from 2 p.m. at Tongilgak on the northern side of Panmunjeom.

The two sides held three rounds of talks at the same place last Sunday, Wednesday and Saturday.

The latest talks are thought to have focused on a possible declaration of a formal end to the Korean War by the two Koreas and the U.S., as U.S. President Donald Trump said Friday that the issue will be discussed at his summit with North Korean leader Kim Jong-un.

Meanwhile, the U.S. ambassador said on Friday during his meeting with South Korean Foreign Minister Kang Kyung-wha that there is still "much work" to do before nailing down the U.S-North Korea summit set for June 12 in Singapore.

Over the past week, Washington and Pyongyang have held a series of talks in Panmunjeom, Singapore and New York to prepare for the summit.

[Photo : YONHAP News]