The Foreign Ministry on Monday officially apologized for the first time for the delayed delivery of a virtual declaration of war before Japan's 1941 attack on Pearl Harbor.
The declaration - a formal notice of the breaking off of talks aimed at averting war - was delivered almost an hour after the surprise attack.Documents declassified on Sunday said the ministry had blundered by failing to give Japan's embassy in Washington sufficient warning of its urgent task.
"It is extremely regrettable that such a thing happened, which we consider inexcusable," ministry spokesman Terusuke Terada said Monday.
In one of the newly disclosed documents, Katsuzo Okumura, a senior embassy counselor at the time, said he was shocked when he heard news of the Pearl Harbor attack on the radio after he finished typing the last page of the declaration.
In the Dec. 7, 1941, air raid on against the U.S. Pacific Fleet, the Japanese killed 2,400 people and destroyed 120 U.S. planes and 19 ships.
President Franklin Roosevelt called it a "date which will live in infamy," and the United States entered World War II the following day.
The ministry says the latest disclosure is the most comprehensive account and the only existing government record of what happened in Washington in the final hours before the attack.
The reports say that even after most of the declaration had been deciphered, since there was no warning of urgency, all the embassy officials gathered at a Chinese restaurant for a farewell party.