Japanese and North Korean government negotiators were unable to reach an agreement on diplomatic recognition during a second round of high-level talks in the Chinese capital Saturday, agreeing only to meet again next month, Japanese officials said.

"Important and substantial issues remain," Japanese Foreign Ministry official Tadashi Iwai said after the talks.Iwai, director of the ministry's Northeast Asia division, would not elaborate on the issues at stake and said only the two sides had agreed to meet again in Beijing for a third round of preliminary talks, "probably in mid-December."

North Korean officials gave the date for the next round of talks as December 15-16, but Iwai said the exact date had not yet been fixed.

Saturday's discussions, which lasted two and a half hours, followed the first such meetings last week aimed at normalizing diplomatic ties between North Korea's reclusive communist government and Japan.

One key obstacle to the discussions is believed to be North Korea's demands for post-1945 war compensation from Japan, according to a Japanese diplomat who described the issue as "the most significant problem" hampering the talks.

The preliminary Beijing talks were designed to agree on a time, place and agenda for full-blown bilateral talks, and also sought to determine the diplomatic level at which subsequent discussions would be held.

But the two sides failed to reach an agreement on any objective despite meetings totaling 5 1/2 hours in the past week, Japanese diplomats said.

The Japanese Foreign Ministry's six-member team was led by Sakutaro Tanino, director general of the ministry's Asian Affairs department.

Informal ties between Tokyo and Pyongyang have been growing steadily over the years.