Japan and the U.S. engaged in negotiations during 1941, attempting to improve relations. In the course of these negotiations, Japan offered to withdraw from most of China and Indochina after making peace with the Nationalist government. It also proposed to adopt an independent interpretation of the Tripartite Pact and to refrain from trade discrimination, provided all other nations reciprocated. Washington rejected these proposals. Japanese Prime Minister Konoye then offered to meet with Roosevelt, but Roosevelt insisted on reaching an agreement before any meeting. The U.S. ambassador to Japan repeatedly urged Roosevelt to accept the meeting, warning that it was the only way to preserve the conciliatory Konoye government and peace in the Pacific. However, his recommendation was not acted upon. The Konoye government collapsed the following month, when the Japanese military rejected a withdrawal of all troops from China.

Japan's final proposal, delivered on November 20, offered to withdraw from southern Indochina and to refrain from attacks in Southeast Asia, so long as the United States, United Kingdom, and Netherlands ceased aid to China and lifted their sanctions against Japan. The American counter-proposal of November 26 (November 27 in Japan), the Hull note, required Japan completely evacuate China without conditions and conclude non-aggression pacts with Pacific powers. On November 26 in Japan, the day before the note's delivery, the Japanese task force left port for Pearl Harbor.

The attack on Pearl Harbor took place before any formal declaration of war was made by Japan, but this was not Admiral Yamamoto's intention. He originally stipulated that the attack should not commence until thirty minutes after Japan had informed the United States that peace negotiations were at an end. However, the attack began before the notice could be delivered. Tokyo transmitted the 5000-word notification (commonly called the "14-Part Message") in two blocks to the Japanese Embassy in Washington. Transcribing the message took too long for the Japanese ambassador to deliver it on schedule; in the event, it was not presented until more than an hour after the attack began. (In fact, U.S. code breakers had already deciphered and translated most of the message hours before he was scheduled to deliver it.) The final part is sometimes described as a declaration of war. While it was viewed by a number of senior U.S government and military officials as a very strong indicator negotiations were likely to be terminated and that war might break out at any moment, it neither declared war nor severed diplomatic relations. A declaration of war was printed on the front page of Japan's newspapers in the evening edition of December 8, but not delivered to the U.S. government until the day after the attack.