Senior North Korean officials and new leader Kim Jong Un pay their respects to Kim Jong Il.

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NEW: The U.S. and South Korean defense ministers talk by phone, a spokesman says

Assistant Secretary for East Asian and Pacific Affairs Kurt Campbell will make the trip

He'll arrive in China, then go to South Korea and Japan

It is the first such visit since the death of North Korean leader Kim Jong Il

Washington CNN  — 

A top U.S. diplomat will travel to three nations around North Korea early next year in the first such talks since longtime leader Kim Jong Il’s death, the State Department announced Thursday.

Assistant Secretary for East Asian and Pacific Affairs Kurt Campbell will “discuss a range of important bilateral, regional and global issues” during his four days in China, South Korea and Japan, the State Department said.

The statement specifically mentions that the “latest developments related to North Korea,” as well as Myanmar, will be on the agenda. Myanmar, also known as Burma, has seen rapid political change – including the legalization of famed dissident Aung Sang Suu Kyi’s political party – since the election of a new president in March.

The announcement about Campbell’s trip came the same day that U.S. Defense Secretary Leon Panetta talked by phone with his South Korean counterpart, Kim Kwan-Jin.

During the roughly 20-minute call, the pair discussed the situation in the Korean peninsula and stressed that maintaining peace and security were their top priorities, Pentagon spokesman George Little said.

This all comes on the heels of the death of communist North Korea’s leader on December 17. Huge crowds gathered Thursday in Pyongyang for a state-orchestrated memorial service a day after his funeral.

During that ceremony, Kim Yong Nam – the president of North Korea’s parliament – declared that Kim Jong Un “is the supreme leader who has inherited (his father’s) beliefs, leadership, courage and guts.”

Campbell’s trip begins Tuesday in Beijing. The U.S. diplomat then will head to the South Korean capital of Seoul for the following two days, before wrapping up January 7 in Tokyo.

Under Kim Jong Il, North Korea suffered a devastating famine, even as it built up its million-strong army, expanded its arsenal of ballistic missiles and became the world’s eighth declared nuclear power.

Pyongyang’s policies and rhetoric often put it at odds with the United States and its ally, South Korea. Washington does not have formal diplomatic relations with Pyongyang, though it has had communications with the reclusive nation, such as through the so-called six-party talks.

In October, U.S. officials held a “positive” meeting with a North Korean delegation in an effort to restart these long-stalled discussions over ending Pyongyang’s nuclear program, U.S. Ambassador Stephen Bosworth said at the time.

North Korea technically remains at war with the South more than five decades after their 1950-1953 conflict, after which an armistice was signed between the two nations. There was never a formal peace treaty. That uncertainty has left the peninsula split by the world’s most heavily fortified border.

Adding to the insecurity are questions about Kim Jong Un, who remains largely an unknown quantity outside his own country.

A delegation of 18 South Korean citizens returned Tuesday from a two-day visit to the north to pay their respects to the fallen leader and meet with his successor, Kim. Seoul has expressed its sympathy to the North Korean people and gave the green light for the visit by the civilian group – which includes Hyundai Group Chairwoman Hyun Jeong-Eun and the widow of former South Korean President Kim Dae-jung.

A day earlier, Japanese Prime Minister Yoshihiko Noda met with Chinese President Hu Jintao in Beijing.

“The two sides believe that maintaining peace and stability of the Korean peninsula serves the common interests of all parties,” Chinese Foreign Ministry spokesman Hong Lei told reporters Monday after the two leaders’ meeting.