WATERTOWN, Mass. (AP) _ Stephen Morris turned up the volume of his television set when someone asked President Clinton about him at a news conference.

Not many people had heard of Morris until the Harvard researcher returned from a trip to Moscow with a Soviet document purporting to show that the North Vietnamese held more American prisoners of war than they admitted.

The Vietnamese government called the document a fabrication and a U.S. presidential envoy said it was full of errors.

''It's a challenging task to take on the array of forces who don't want to face up to this and want to discredit this,'' Morris said.

The 44-year-old Australian citizen has been deluged with telephone calls and mail after making the report public.

The Soviet report that Morris unearthed in the archives of the former Central Committee headquarters is based on a North Vietnamese army general's 1972 assertion that Hanoi held 1,205 American prisoners of war at a time when it admitted having only 368.

The archive director was fired last week for letting Morris see the top- secret document. Natalya Krivova, spokeswoman for the State Archives Service, said the document was believed authentic, but refused to speculate about the reliability of its contents.

Morris gave a copy to the Department of Defense last week.

''I believe this document indicates a deliberate policy of duplicity by the Vietnamese government,'' Morris said. ''The intention is to deceive the United States about how many prisoners they were holding, to use them as bargaining chips to get everything they need.''

Morris said he was heartened when Clinton said: ''I cannot say I'm fully satisfied that we know all there is to know.''

The envoy, retired Gen. John Vessey Jr., told Clinton on Wednesday there were many flaws in the document.

Morris, a visiting scholar at Harvard's Center for International Affairs, has long been a critic of Vietnam's communist government ''on moral grounds.''

In published articles, he has said he was in favor of gradual normalization of relations between the two countries. Now Morris said the document he found has changed his mind.

''I couldn't believe what I was reading,'' he said. ''My feeling was that this was the end of normalization for the time being.''

If the document is mistaken, Morris said, ''there are only two possibilities: One, that the Vietnamese deliberately fed the Russians false information in the middle of a war in which they were dependent on Soviet goodwill - and that the Soviets fell for it.

''The other possibility was that Gen. (Tran Van) Quang received false information from his subordinates.''

The Vietnamese want humanitarian aid from the United States and U.S. business interests hope for access to Vietnamese markets.

Asked if he believes there still are American servicemen alive in Vietnam, Morris said:

''I just don't know. We can only speculate,'' he said. ''I only have the beginning of the story, not the end.''