The Democratic People's Republic of Korea plans to hold the launch between April 12 and 16, part of celebrations to mark the birth centennial on April 15 of its national founder Kim Il-sung.

Japan on Saturday deployed missile batteries in Tokyo and has dispatched destroyers carrying interceptor missiles, reportedly to the East China Sea, to intercept the DPRK 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.

The 38 North website, a US site on DPRK analysis, said during the weekend that an April 4 photo of the launch site at Tongchang-ri, in the DPRK's northwest, indicated the first stage of the rocket, while not visible, may be placed in the gantry.

Washington called the launch a cover to test missile systems that could target parts of the US, while Pyongyang said the rocket will carry a satellite into orbit to study crops and natural resources.

The DPRK has invited foreign experts and more than 30 foreign reporters to observe the launch. Visitors started to arrive in Pyongyang during the weekend.

Zhou Yongsheng, a professor of Japanese studies at China Foreign Affairs University, said the agreement of the three ministers and the relatively constrained wording of the Japanese and ROK diplomats showed Tokyo and Seoul are willing to "quench fires".

"It is likely that China has advised Japan and the ROK to avoid conflict, and the two might have asked Beijing to persuade Pyongyang to cancel the launch," Zhou said.

However, Zhou said the chances of Pyongyang canceling the launch are quite slim.

"But as long as the rocket follows the route Pyongyang announced earlier, it will not pass Japanese or ROK territory and conflict will be avoided," he said.

Zhang Liangui, an expert on Korean studies at the Party School of the Communist Party of China Central Committee, said the remarks by Japanese and ROK ministers showed that they don't want to play up tension on the peninsula, although their stance on the matter has not changed.

Pyongyang has conducted three such launches since 1998. The last launch, in 2009, led to UN condemnation and the DPRK walking away from the Six-Party Talks focusing on nuclear disarmament. Weeks later, Pyongyang carried out a nuclear test.

DPRK study expert Masao Okonogi, from Japan's Kyushu University, warned in an AFP report on Sunday that Pyongyang could carry out another nuclear test in response to international condemnation of its launch.

Trilateral FTA

Trade issues were also raised during the Sunday meeting.

A trilateral investment agreement is likely to be signed when the leaders of the three nations meet later this year, the Japanese foreign minister said on Sunday.

Negotiations on the agreement, which started in 2007, finished in March, paving the way for a free trade agreement which will cover one-fifth of the world's trade volume.

A press release issued by the Foreign Ministry on Sunday also said the three countries agreed to start negotiations on a trilateral FTA "as soon as possible". East Asian nations should cooperate, especially with an uncertain global economy, Yang said.

AP and AFP contributed to this story.