Top U.S. diplomat in China to discuss North Korea

• The diplomat is visiting China, South Korea and Japan in a four-day trip
• He will discuss North Korea, Myanmar and other issues during his visit
• The situation on the Korean peninsula is tense following the death of Kim Jong Il
• North Korea has dismissed the idea of a change in relations with the South

(CNN) -- A top U.S. diplomat will arrive in Beijing on Tuesday at the start of a tour around Northeast Asia, which is still adapting to the change of leadership in North Korea following the death of Kim Jong Il last month.

During the four-day visit, Kurt Campbell, the assistant secretary for East Asian and Pacific affairs, is stopping off in China, South Korea and Japan, all close neighbors of nuclear-armed North Korea.

Relations on the Korean peninsula have been tense since Kim's death fueled doubts about the secretive regime's stability and future direction.

Funeral and memorial services for Kim in Pyongyang last week served to cement the rise of his son and chosen successor, Kim Jong Un, as the nation's "supreme leader."

President Lee Myung-bak of South Korea on Monday called the transitional period following the elder Kim's death a "window of opportunity" to improve relations across the world's most heavily fortified border.

But Pyongyang has so far dismissed the notion that a new leader will bring about any shift in its stance toward its neighbor to the south.

"The South Korean puppets and foolish politicians around the world should not expect any change," the North Korean National Defense Commission warned in a statement last week, labeling Lee's government a "group of traitors."

Against that backdrop, Campbell's visit aims to cover "a range of important bilateral, regional and global issues" including North Korea, according to the State Department. He begins Tuesday by meeting senior officials in China, a key ally and economic partner of North Korea.

Campbell will then leave Wednesday for South Korea, where nearly 30,000 U.S. troops are stationed. His last stop is in Japan, another key U.S. military ally.

All three countries that Campbell is visiting have participated in the so-called six-party talks over ending North Korea's nuclear program. The other participants are the United States, Russia and North Korea itself.

In October, U.S. officials held a "positive" meeting with a North Korean delegation in an effort to restart these long-stalled discussions, U.S. Ambassador Stephen Bosworth said at the time.

Kim's death has left the future prospects of that initiative uncertain.

As well as North Korea, Campbell's meetings will address the topic of Myanmar, which 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.

China has been one of Myanmar's key supporters and trading partners during the Southeast Asian nation's decades of military rule.