Following trilateral talks in the eastern Chinese city of Ningbo, the foreign ministers of Japan and South Korea both said a launch by North Korea would violate U.N. Security Council resolutions—indicating their belief that the North should face sanctions if it goes through with the plan.
But China, the North's closest ally, instead urged more dialogue and communication.
"The Chinese side is troubled by the developments, and strongly encourages everyone involved on all sides, at high and low levels, to remain calm and reasonable," Chinese Foreign Minister Yang Jiechi told reporters. "These issues need to be worked out in a diplomatic and peaceful manner."
Japan's Kyodo News service reported that Foreign Minister Koichiro Gemba said the three sides failed to reach a consensus on the launch, an apparent reference to China's softer approach.
"We were able to increase our common views," Kyodo quoted Gemba as saying. "But frankly speaking, I would not say the three countries completely shared the same view."
Gemba said the key result of the talks was a commitment by all sides to continue to work together to stop the launch.
There have been fears in Japan and South Korea that debris could fall from the rocket, expected to be launched in the coming week. Japan's defense minister has ordered missile units to intercept the rocket if it or its fragments threaten to hit Japan. Seoul has also warned it might shoot down any parts of the rocket heading for its territory.
North Korea says the rocket will carry a satellite into orbit to study crops and natural resources. Washington and others call the launch a cover to test missile systems that could target parts of the United States and elsewhere.
The North Korean launch is meant as a showcase of national power and technology during celebrations of the centennial of the April 15 birth of national founder Kim Il Sung. While North Korea has conducted tests of two nuclear devices, analysts don't believe it has yet mastered the technology needed to shrink a nuclear weapon and mount it on a missile.
North Korea has conducted three such launches since 1998. The last launch, in 2009, led to U.N. condemnation. The North then walked away from six-nation nuclear disarmament talks, and weeks later carried out its second nuclear test.