In a stunning admission that cast new doubts on the authenticity of the purported secret diaries of Adolf Hitler, British historian Hugh Trevor-Roper today backed away from his earlier conviction that the documents are genuine.

At a three-hour press conference intended by the West German newsweekly Stern to quash speculation that the diaries are fraudulent, Trevor-Roper instead said there had been "a misunderstanding" with the magazine's editors. He now felt, he said, that no clear link has been established between the 60 volumes and the crash, toward the end of World War II, of a plane that some historians believe was carrying Hitler's personal papers.

"A final judgment cannot be given until the whole text has been examined," he said. "As a historian I regret that this process has been sacrificed to the requirements of the journalistic scoop."

Trevor-Roper said that the London Sunday Times, which printed excerpts over the weekend, would cease further publication of the diaries until they were fully verified. The historian serves on the board of Times Newspapers Ltd. In London, a statement released by the Times management indicated, without directly saying so, that nothing further will appear until the doubts are resolved.

Revelation last week that Stern had discovered Hitler's secret diaries was hailed as one of the most significant historical events of the decade. Despite widespread skepticism among German experts, the claim acquired credibility because Trevor-Roper had examined the papers and pronounced them legitimate.

The British historian, however, said today that he only had the chance to scrutinize the handwriting of several samples but "was not given the opportunity to read the stuff." In an article in Saturday's London Times, Trevor-Roper had declared himself "satisfied that the diaries are authentic."

An American specialist on Hitler, Gerhard Ludwig Weinberg of the University of North Carolina, who also checked some of the writing samples, voiced caution today about the diaries. He said that the entries should be examined by independent handwriting experts as well as scholars who might explore what he called "contextual absurdities."

Stern insists that the Hitler diaries were flown out of Berlin in the last days of the war as the Nazi dictator prepared to shift his headquarters to his Bavarian Alpine retreat in Berchtesgaden.

Historians believe that the plane, which was later said by Hitler's personal pilot to have been carrying the dictator's personal papers, crashed in flames after being shot down by the allies near Boehnersdorf in what is now East Germany.

Stern's editor-in-chief, Peter Koch, said today that the diaries emerged unscathed because they were locked in a metallic, zinc-lined box. Later they were discovered by a Wehrmacht (Army) officer who hid the papers for many years in a hayloft.

Trevor-Roper said that he was under the impression as he perused the diaries in the back room of a Zurich bank that Stern's editors had satisfactorily confirmed a link between the papers and the cargo aboard the doomed plane.

Today, however, he expressed dismay that the West German journalist who acquired the documents, Gerd Heidemann, refused to provide any information, even to his editors, about where and from whom he received the diaries.

Heidemann claims he cannot reveal the connection between the crash site and the cache of papers to protect citizens in the East Bloc who helped him from retribution by the state.

He will only say that the hunt for the diaries led him on a long odyssey through Austria, Switzerland, Spain and South America where he interviewed Nazi fugitives, including Klaus Barbie, the so-called "Butcher of Lyons" who was recently extradited from Bolivia to France.

Heidemann says he ultimately learned the identity of the Wehrmacht officer, located him and persuaded him to give him the diaries for an undisclosed sum of money.

Koch said, "We believed he was working fair ly and honestly and felt we had to trust him." He added that he could not even discuss the reasons why information about the diaries' background must be kept secret "because that would divulge too many hints about the source."

Trevor-Roper said he thought Heidemann had told Stern's editors exactly how the diaries were obtained. He said that on Sunday, when he learned this was not the case, "I pressed Heidemann rather severely, but he proved unwilling to provide any evidence."

Trevor-Roper said that because Heidemann does not feel free to reveal his source, even to Stern's editors, "the link between the plane and the papers is rather more shaky."

He said that "there are a large number of forgeries on the gray market going for a high price these days and it is always possible for one man to be deceived."

The only way to resolve doubts, he said, was to submit the entire text of the diaries to handwriting experts and Hitler-era scholars in West Germany.

Stern originally intended to publish the volumes over 18 months before turning them over to West Germany's federal archives, but Koch admitted that the current controversy may require the magazine to accelerate the schedule.

Both Trevor-Roper and Weinberg urged Stern to submit the diaries as soon as possible to independent German scholars, who were not consulted before the magazine decided to print extracts and sell rights.

Koch said that the German academic community was avoided because of the need to prevent news leaks about the controversial diary and what he described as the questionable record of some German specialists in assessing Hitler memorabilia.

A more transparent motive, however, appears to be the almost unanimous belief among West German experts that the diaries are forged.

Such noted Hitler experts as Karl Dieter Bracher of Bonn University and Martin Broszat of the Munich Institute for Contemporary History expressed deep skepticism about the diary's revelations.

Prof. Werner Maser, who has studied Hitler's writings and career for several decades, claims there is a virtual cottage industry in Potsdam, East Germany, that deals in faked pictures and papers from the Hitler era.

British historian David Irving, who intervened at today's press conference to protest that the diaries were outright fakes, claims that he examined several volumes of Hitler papers last year but dismissed them as forgeries because of what he termed blatant historical errors.

He said Hitler lost use of his right arm after Army officers tried to assassinate him. But the Stern diaries contain entries by Hitler mocking his would-be assassins right after their failed attempt on his life.

The German press and public seem to share such cynicism about the Hitler diaries. Television and newspapers here barely noted the Stern scoop, after months of saturation coverage of the Hitler era commemorating the 50th anniversary of the dictator's rise to power.

The federal government dismissed the idea today of setting up an independent commission to investigate the diaries. A spokesman, somewhat sarcastically, said the government was more concerned with formulating its foreign and economic policies than with studying diaries.