South Korea's defense chief called Wednesday for a pre-emptive strike on North Korea if there is a clear indication the country is preparing a nuclear attack.

The comments, made as the two sides held a second day of talks on further developing their joint industrial complex in the North, were likely to draw an angry reaction from Pyongyang, which recently issued its own threat to break off dialogue with Seoul and attack.

South Korea should "immediately launch a strike" on the North if there is a clear intention of a pending nuclear attack, Defense Minister Kim Tae-young said at a seminar in Seoul.

Kim made similar remarks in 2008 when he was chairman of South Korea's Joint Chiefs of Staff, prompting North Korea to threaten to destroy the South.

The North, which conducted underground nuclear tests in 2006 and 2009, claims its nuclear weapons are not for use against South Korea but are a security guarantee against what it calls U.S. hostility.

Despite the rhetoric, officials held follow-up discussions Wednesday on the industrial complex in the North Korean border city of Kaesong, according to Seoul's Unification Ministry. It did not provide further details.

The South Korean delegation was scheduled to return home later Wednesday, Unification Ministry spokesman Chun Hae-sung said. On Tuesday, the two sides met for nearly four hours to assess a joint tour of industrial parks in China and Vietnam undertaken in December.

Kaesong, which combines South Korean capital and technology with cheap North Korean labor, is the most prominent symbol of cooperation between the two countries still technically at war. About 110 South Korean factories employ some 42,000 North Korean workers.

The complex came under a cloud in late 2008, however, when North Korea tightened restrictions on border crossings amid growing tensions between the two countries.

This week's talks come just days after Pyongyang threatened to launch a "sacred nationwide retaliatory battle" and vowed to cease all communication with the South following reports of a South Korean contingency plan to handle unrest in the isolated North.

The Korea Institute for National Unification, a state-run think tank in Seoul, speculated in a report posted on its Web site late Tuesday that North Korea leader Kim Jong Il would not rule the country beyond 2012. The think tank said a military coup, a popular uprising, massacre or mass defections could occur in the post-Kim era.

Kim, 67, is believed to be grooming a son to take over as leader of the nation of 24 million.

Meanwhile, South Korea's top nuclear envoy, Wi Sung-lac, left for the U.S. on Wednesday for talks with Stephen Bosworth, Washington's special U.S. envoy to North Korea, and other U.S. officials.

North Korea recently has demanded that international sanctions be lifted before it returns to stalled negotiations aimed at ending its nuclear weapons programs.

The North also has called for a peace treaty to formally end the Korean War, saying the agreement would help end hostile relations with the U.S. and promote the denuclearization of the Korean peninsula. The three-year conflict ended in a truce, not a peace treaty, in 1953.

The U.S. rejected the North's demand and urged Pyongyang to rejoin the disarmament negotiations.

"It would be inappropriate at this juncture to lift sanctions," Assistant Secretary of State Kurt Campbell told reporters Tuesday in Washington. "We think that the appropriate next step is for North Korea to return to the six-party talks and to resume deliberations in this context."

Pyongyang quit the talks — which also involved China, Japan, Russia, South Korea and the United States — in anger over international condemnation of its long-range rocket launch last April. The regime carried out its second underground nuclear test the following month.

Also Tuesday, the U.S. and Japan issued a joint statement reaffirming their cooperation with other nations to "deal with the threat from North Korea's nuclear and missile programs as well as to address humanitarian issues," according to the U.S. State Department.