North Korean leader Kim Jong-il's son and heir Jong-un is to visit China in March or April, the Sankei Shimbun reported Tuesday.

A likely timeframe is between March 14, the day when the Chinese People's Political Consultative Conference and the National People's Congress end, and April 15, North Korean regime founder Kim Il-sung's birthday.

The Sankei said Pyongyang and Beijing have already started fine-tuning the schedule with this timeframe in mind.

There are claims that in October last year, Zhou Yongkang, a member of the Politburo Standing Committee of the Chinese Communist Party, delivered a letter from Chinese President Hu Jintao to Kim Jong-il inviting the new North Korean leadership, including Kim Jong-un, to visit China at a convenient time.

Another rumor has it that the invitation was sent through Choe Tae-bok, a Workers Party secretary who visited China last September.

If Kim junior visits China, he will probably seek assurances that he has Beijing's backing as his father's successor and hold out his hand for economic aid. He would probably meet Chinese Vice President Xi Jinping.

But it seems likely that his visit will be kept under wraps.