BEIJING — South and North Korea will not march together in tomorrow’s opening ceremony of the Beijing Olympics.

The IOC president, Jacques Rogge, said today that negotiations for a joint march failed, calling it a “setback for peace” and reunification efforts on the divided peninsula.

Athletes from the two Koreas marched together in the same uniform under the blue and white “unification flag” at the 2000 Sydney Olympics and 2004 Athens Games.

“We’ve tried to have this in Beijing,” Mr. Rogge said. “Unfortunately, it was not possible.”

He said there had been a “great willingness” among the two national Olympic committees for a joint march.

“Unfortunately the political powers — both on the South and the North — did not agree,” he said. “And I regret this very much because this is a setback for peace and harmony and reunification.”

Mr. Rogge said he had sent two personal letters to the presidents of both Koreas urging a combined march.

“The IOC has to respect the sovereign decision of governments and this is definitely something that both people wanted, but they, in their country, are also under their government,” he said.

The two sides fought the 1950-53 Korean War that ended with a truce, not a peace treaty, leaving them still technically at war.

Reconciliation talks have been suspended since South Korea’s conservative new president, Lee Myung-bak, assumed office in February with a harder-line stance on Pyongyang.

The two Koreas had earlier discussed forming a unified team, but the negotiations fell apart due to differences on how to select athletes. The South insisted they be selected based on performance, while the North demanded equal representation.