Former secretary of state Henry A. Kissinger "vastly overstated, at least by implication," the extent to which hitherto classified information had been cleared for publication in his memoirs, according to correspondence made public yesterday.

The assessment was made by an official of the National Security Council in response to an inquiry by the publishers of another book whose author was successfully sued by the government for failing to obtain proper clearance.

Kissinger, in the foreword of his book "The White House Years," wrote that "treatment of classified materials in this book has been worked out with the office of the national security adviser, Dr. Zbigniew Brezezinski, to whom I express my appreciation."

On May 21, however, the staff secretary of the NSC, Christine Dodson, wrote to the head of the publishing firm Random House that Kissinger submitted only "a very small part of the manuscript" for review, and this was "in the form of disconnected, brief exerpts."

After some "required changes" were specified, she wrote, "Kissinger never submitted any further materials for review. It is our judgment, therefore, that the passage you quote from the book's foreword vastly overstates, at least by implication, the degree of classification review to which the book was subjected by Dr. Brzezinski's office.'

The NSC letter was sent to Robert L. Bernstein, president of Random House, which had published "Decent Interval," a book by former CIA officer Frank Snepp critical of American policy in Vietnam.

In a far-reaching ruling in February, the Supreme Court held that Snepp had breached his position of trust with the CIA by failing to submit the book to the agency for prepublication review.

The court majority also said that "even in the absence of an express agreement" such as the one Snepp signed with the CIA, the government can impose restrictions on the release of confidential information, even when no government secrets are compromised.

Snepp has been ordered to relinquish his profits from the book, which are currently estimated at about $140,000.

Kissinger, who is expected to make about $5 million from his book, could not be reached for comment. "The White House Years" was published last fall by Little, Brown & Co. Kissinger owns the worldwide book and serialization rights.