US Secretary of State John Kerry Thursday welcomed new high-level talks between North and South Korea, while warning Pyongyang against trying to derail an upcoming South Korea-US military exercise.

US Secretary of State John Kerry Thursday welcomed new high-level talks between North and South Korea, while warning Pyongyang against trying to derail an upcoming South Korea-US military exercise.

Kerry, in Seoul to discuss North Korea's nuclear program at the start of an Asia tour, stressed that the US would never accept the North as a nuclear state and that it would not be drawn into "talks for talks' sake" with Pyongyang.

"We've been through that exercise already, we want to know that it's real," he said, adding that North Korea had to take "meaningful action" towards denuclearization before a dialogue could begin.

At the same time, he voiced full support for South Korean President Park Geun-Hye's efforts to build trust with the North, and welcomed a recent diplomatic initiative that saw the rival Koreas meet Wednesday for their highest-level talks in seven years.

A second round of discussions is scheduled for Friday, with North Korea pushing the South to postpone its annual military exercises with the US until after a planned reunion from February 20-25 of family members separated by the Korean War.

The drills are slated to begin February 24 and Seoul is refusing to consider a postponement -- a stance that Kerry made clear had Washington's backing.

Kerry said the reunion was a purely humanitarian issue and there was "no legitimate excuse" for linking it to the military exercises that take place every year.

North Korea should act out of "human decency" and not try and use "one (issue) as an excuse to somehow condition the other", he added.

Last year's joint exercises fuelled an unusually sharp and protracted surge in military tensions, with Pyongyang threatening a pre-emptive nuclear strike, and nuclear-capable US stealth bombers making dummy runs over the Korean peninsula.

North Korea views the drills as a rehearsal for invasion, and has repeatedly demanded their permanent cancellation.

The United States has around 28,000 troops stationed in South Korea.

Under its defense agreement with Washington, South Korea is protected by the US nuclear umbrella and the United States would assume overall operational command of joint US and South Korean forces if a full-scale war with the North broke out.