If the world's poorest countries harbor high expectations about any fresh trade concessions from industrialized countries at a key international conference in May, Japan will probably turn out to be a real letdown.

Kofi Annan, the United Nations secretary general, sent letters to Prime Minister Yoshiro Mori and leaders of the other major industrialized countries recently, asking them to take the political leadership in opening their markets further to imports from the world's poorest countries.

In the letters, which came ahead of the third U.N. Conference on the Least Developed Countries, to be held in Brussels for one week starting May 14, Annan specifically asked the industrialized countries' leaders to do away with tariffs and quotas on more of their imports from LDCs.