US President Barack Obama's defence chief began a visit to South Korea on Monday aiming to show strong support for its military ally locked in a bitter feud with North Korea over a deadly torpedo attack.
Defense Secretary Robert Gates will be joined later in the week by Secretary of State Hillary Clinton for a high profile meeting in Seoul to respond to the North and to discuss ways to deter it from any future attack. But the unprecedented meeting of top diplomats and defence officials between the allies risks angering China, with an expected announcement of US South Korean military exercises that have set off alarms in Beijing.
Tension between North and South Korea remains high following the March sinking of the warship Cheonan, killing 46 South Korean sailors. Pyongyang has denied responsibility and escaped censure this month from the United Nations, which condemned the attack but, in deference to China, did not directly blame North Korea.
North Korea held the first meeting with US led United Nations Command last week to talk about the Cheonan incident. The two sides were expected to schedule a new session to set up a meeting of generals.
North Korea is also sending its foreign minister to a regional forum in Hanoi on Friday, attended also by the United States and China, where the South is expected to make another push for Pyongyang to admit responsibility.
US Assistant Secretary of State Kurt Campbell said the talks in Seoul were aimed at assessing the next steps with North Korea, including whether and how to resume stalled talks about Pyongyang's nuclear programme. North Korea said this month it was willing to return to disarmament talks, in limbo since 2007.
US officials said the visit was meant to show US South Korean unity 60 years after the outbreak of the 1950 1953 Korean War. The Koreas technically remain at war, since the conflict ended with an armistice and not a peace treat. Gates will on Tuesday meet some of the 28,000 US troops stationed in South Korea.
The trip will culminate Wednesday in the first so called "two plus two" talks between the US and South Korean secretaries of defense and state. US officials say the top level event shows the importance President Barack Obama places on ties with South Korea, Asia's four largest economy.
Gates and Clinton are expected to announce a series joint US South Korean military drills over a period of months in both the Yellow Sea and the Sea of Japan, meant to send a message of deterrence to the reclusive North. They also aim to improve South Korea's anti submarine warfare capabilities.
China, North Korea's sole ally, has voiced deep concerns about any US South Korean drills in the Yellow Sea, which separates China and the Korean peninsula, and urged regional powers to put the Cheonan incident behind them.
But the United States has dismissed those concerns, arguing the drills will take place in open, international waters. It said on Monday it will deploy an aircraft carrier to South Korea to participate in the exercises, a major projection of US military power that could deepen anxiety in China.
The 97,000 ton USS George Washington will arrive in the South Korean port of Busan on July 21, during the high level talks in Seoul. It will then head to the first of the drills.
Several US destroyers will also visit Korean ports.
"We thought it was a good idea to move the George Washington into position to make a port call in Korea in time (for the Clinton, Gates) visit," said Pentagon Press Secretary Geoff Morrell, while flying with Gates to Seoul.
"This is a visible, a tangible manifestation of our steadfast commitment to the security of the Republic of Korea."