Japanese trade officials expressed strong concern Friday over Washington's failure to clarify the process leading up to the recent levying of dumping charges on Japanese supercomputers.

During bilateral review talks on the 1990 U.S.-Japan agreement on supercomputer procurement Friday in Tokyo, the Japanese side demanded that the U.S. clarify facts concerning the process of supercomputer purchases by the University Corporation for Atmospheric Research.

UCAR, an affiliate of the federally funded National Science Foundation, had initially tried to buy NEC supercomputers but gave up after the U.S. Department of Commerce raised dumping concerns over NEC products, according to Japanese government officials. Japan asserts that the Commerce Department's intervention was made long before Cray Research Inc., NEC's rival in the bidding, filed such a complaint. This, Japan upholds, would constitute an unjustifiable government involvement in private business.

Late last month, Japan submitted to the U.S. side a series of questionnaires demanding an explanation. The U.S. delegates, however, withheld a response Friday, noting that they did not have enough time to prepare and that the NEC supercomputer case is now pending in a U.S. court. The U.S. side said it will further study the questionnaires and respond in writing in due time, according to a Japanese official.

Asked about possible further action, the official said that the government will wait for Washington's response before making any decisions.