North Korea said on Monday it would "never deal with" South Korean President Lee Myung-bak in a statement carried by Xinhua news agency.
North Korea's National Defense Commission said Lee and his government were undermining efforts to reunify the two nations.
Tensions have been high between the two Koreas in the wake of two deadly incidents last year.
South Korea has accused Pyongyang of sinking its Cheonan warship last March, with the loss of 46 lives. Four South Koreans were killed when North Korea shelled a border island in November.
Six-nation talks aimed at ending Pyongyang's nuclear program have also been stalled for months.
Today, the army of managers is earnestly believing that one can take the man responsible for the licensing of alcoholic beverages, and put it on licensing, and even to supervise the nuclear reactor.
Christophe Behar
We are preparing now a review of these design options and the decision has to be made in 2012, by the public authorities. ASTRID basic and detailed design will be launched afterwards.