The United States said Sunday it has invited a top North Korean envoy to New York for "exploratory talks" on the possible resumption of the six-party negotiations on denuclearization.

Secretary of State Hillary Clinton said the North's vice foreign minister and former nuclear negotiator, Kim Kye-Gwan, would visit the U.S. at the "end of next week".

The United States said Saturday it was "encouraged" by surprise talks between North and South Korea over Pyongyang's nuclear program, but remained cool on resuming disarmament talks.

U.S. Secretary of State Hillary Clinton told regional foreign ministers at an Asian security forum in Indonesia that the onus remained squarely on the North to prove its sincerity before the stalled six-party talks could resume.

North Korea is grappling with an unfavorable situation but the regime's tight grip on its people will prevent any Arab-style uprising, South Korea's defense minister said Wednesday.

"The state of affairs in the North is indeed inauspicious and anything can happen there," Kim Kwan-Jin told a forum, without elaborating.

The architect of Pakistan's nuclear weapons program claims North Korea paid bribes to senior Pakistani military officials in return for nuclear secrets in the 1990s, the Washington Post said Wednesday.

The Post said documents released by nuclear scientist Abdul Qadeer Khan purportedly show him helping to transfer more than $3 million to senior officers, who he says then, approved the leak of nuclear know-how to Pyongyang.

North Korea threatened on Wednesday to launch "a retaliatory sacred war" against South Korea for alleged slander as the two sides held rare talks on a stalled joint tourism project.

A Pyongyang government spokesman accused the South's front line army units of displaying slogans slandering the North's "army, system and dignity" and said they are "little short of a clear declaration of war".

The U.S. commander in South Korea said Monday that North Korea is likely to launch more military attacks against the South, but Seoul and Washington are better prepared to counter the threat.

"While the Kim (Jong-Il) regime has proven a willingness to escalate in order to obtain what it wants, I am convinced that the ROK (South Korea)-U.S. alliance is prepared," General Walter Sharp told a forum.

South Korean troops fired at a passenger jet flying from China with 119 people on board after mistaking it for a North Korean aircraft, amid increasingly fraught relations on the divided peninsula.

Soldiers manning a guard post on Gyodong Island, just 1.7 kilometers south of the North Korean coast, fired their K-2 rifles on Friday towards the plane, descending as it approached Seoul's Incheon International Airport.

South Korean authorities Friday rejected North Korea's demand to send back nine refugees from the communist state, an issue that could further chill frosty relations.

The three men, two women and four children crossed the Yellow Sea border last Saturday in two small boats, with the North's Red Cross warning Thursday that relations could worsen unless the South immediately sends them back.

South Korea's military must retaliate "strongly and thoroughly" if North Korea attacks again, President Lee Myung-Bak said Wednesday.

He made the remarks in a speech read out on his behalf at the inauguration of a new military command, created to bolster defenses on islands near the disputed Yellow Sea border.

The U.S. Navy intercepted a North Korean ship suspected of carrying missiles or other weapons to Myanmar and made it turn back, a senior U.S. official said Monday.

The comments by Gary Samore, special assistant to President Barack Obama on weapons of mass destruction, confirmed reports of the incident, which happened last month, in The New York Times and South Korean media.