They say the American complaints stem from the elections in the United States this year.
The commission is giving foreign defendants only five minutes each to rebut more than 30,000 pages of American complaints.
Important changes were made that addressed previous American complaints.
To the Japanese, the American complaints come across as poor sportsmanship.
The two leaders did said they had established "processes" for discussing American complaints.
The principal American complaint is that the four have obtained unusual trade advantages by holding down the value of their currencies.
Moreover, he said, Cuban officials have refused even to discuss American complaints seriously.
The trade group agreed with the American complaint earlier this month, although it reduced the amount of damages sought from an original $500 million.
But the umpires, following closely in a powerboat, overruled the American complaint.
For Chinese officials who listened patiently to American complaints today, the response was not too subtle.