The milder comments in Rodong Sinmun, a newspaper of the ruling communist party, came one day before US President Barack Obama is due to start a visit to South Korea expected to focus on North Korea issues.

Rodong and other official newspapers had last week vowed that the South would pay dearly for the November 10 exchange of fire, in which a North Korean patrol boat was set ablaze.

The South said the North's boat crossed the border despite repeated warnings and opened direct fire in response to warning shots. The North said the South's navy staged a premeditated provocation.

"It entirely depends on the attitude of the South Korean authorities whether or not inter-Korean relations continue to deteriorate," Rodong Sinmun said Tuesday, as quoted by the official Korean Central News Agency.

"We will continue to make active efforts, as we did before, for the improvement of North-South relations."

The paper said ties could not be normalised in a situation where "one party distrusts its dialogue partner and escalates confrontation and even carries out a military provocation..."

It added: "Nothing but war will break out in a situation of mutual hostility and escalating military tension."

The naval clash, the first for seven years, followed recent peace overtures from Pyongyang to both Seoul and Washington.

Some analysts suspect the North wanted to strengthen its bargaining hand in upcoming talks with the United States by raising tensions on the peninsula.

The US special envoy for North Korea, Stephen Bosworth, is to visit Pyongyang by the end of this year to try to bring it back to six-nation nuclear disarmament talks.

China and the United States want the six-party talks to resume as soon as possible, Obama said Tuesday after meeting President Hu Jintao in Beijing.

South Korean Foreign Minister Yu Myung-Hwan said in Seoul he hopes Bosworth's trip would quickly revive the six-nation talks.

The North quit the forum in April and staged its second atomic weapons test the following month, attracting tougher United Nations sanctions.

The United States says Bosworth's only goal is to bring the North back to the six-party talks, which also group China, Japan, Russia and South Korea.

Yu said the North may have various reasons for seeking bilateral talks and one of them "may be to disrupt the unity among the five nations", which support the UN sanctions.

But the minister said he expects "no substantive negotiations" during Bosworth's visit.

North Korea has said it is ready to return to the six-nation talks but only if there is progress in the bilateral discussions.

Yu said he expects Bosworth to visit sometime between Thanksgiving Day on November 26 and Christmas Day.