AP

KURT CAMPBELL, a man who would not look out of place on an American football field, likes sporting metaphors. America's assistant secretary of state for East Asian and Pacific affairs reckons a “game plan” is being developed by America and South Korea over how to deal with North Korea in coming months. South Korea called on Monday July 20th for new efforts to persuade North Korea to end its nuclear-arms programme.

American officials too are “in the midst of putting in place a series of actions…that are designed to put more pressure on North Korea” to give up its nuclear bombs, Mr Campbell told reporters in Seoul. United Nations sanctions aimed at stopping North Korea from earning money by selling arms, Mr Campbell claims, has caused “some pain to the leadership” in North Korea.

But before Mr Campbell arrived in South Korea, a North Korean diplomat rejected suggestions that sanctions against his country would succeed. “We've been living under sanctions for over half a century,” said Pak Tok Hun, deputy chief of North Korea's United Nations diplomatic mission. “We'll continue to live the way we always have.”

Mr Campbell is undeterred by Mr Pak's assertions. He gave warning of further hardship for the North Korean people and isolation for its regime. Mr Campbell's message resonates with South Korea's president, Lee Myung-bak. Mr Lee has rejected the reconciliation and engagement of his predecessors toward North Korea.

But Mr Lee has not been able to discard all of the past. The Kaesong industrial complex, just across the heavily fortified border in North Korea, remains in operation. It is used by more than 100 South Korean companies as a cheap manufacturing base. Kaesong is an important source of cash for North Korea. South Korea's Unification Ministry says Mr Lee wants to develop Kaesong further. That may clash with Mr Campbell's goal of increasing North Korea's isolation. Asked whether the American government supports Kaesong, Mr Campbell demurred.

South Korea's government and corporations have invested 799 billion won ($634m) in developing Kaesong's infrastructure and paid $16m to North Korea for the right to use the land. Politics and business must be separate, says Park Jung-won of the Corporate Association of the Kaesong industrial complex. South Korea and North Korea are like China and Taiwan when it comes to their political relationship in that they “fight like cats and dogs,” says Mr Park. But in business Taiwan and China co-operate. Both Koreas should use the pragmatic relationship across the Taiwan Strait as an example and develop Kaesong further, according to Mr Park.

But North Korea has used this island of capitalist endeavour in its midst as a political bargaining chip. It cut transport links across the border with the south in March, has demanded an additional $500m for land use and wants its salaries for its workers increased from about $50 a month to $300. South Korea has rejected demands to pay higher wages or for a revised land use fee.

Of more concern to South Korea is the kidnapping by North Korea of one of its businessmen in March. North Korea refuses to discuss the man's imprisonment with South Korea's government. It claims that the man, identified only as “Mr Yu”, tried to lure a North Korean female worker to the south and insulted the North Korean regime.

The kidnapping prompted a South Korean company to leave Kaesong, the first to do so. The remaining firms are using a minimum number of South Korean staff at the industrial park, fearful that others could be taken as hostages too. But Mr Park says that stories of a crisis at Kaesong are exaggerated.

Mr Campbell has discussed Kaesong with South Korean officials. South Korea's government is eager to show its unflinching support toward its most important ally. So, as a co-operative business relationship, albeit sometime fraught, Kaesong poses a problem when increased isolation and tougher sanctions are the order of the day. South Korea's unification ministry says it wants “to turn the direction of [this] inter-Korean relationship…toward dialogue and openness.” Mr Campbell may not be so eager.