LONDON, 18 September 1939, 10.08 p.m.
Received 19 September 1939
FAR EAST 1. United States Under Secretary of State  has informed the French Ambassador  that should France and Great Britain withdraw their troops from China on grounds of belligerency in Europe, as suggested by Japan, United States Government would be unable, in view of opposition from the Congress, to send troops to China to protect concessions in the event of war. Commitment to action was one thing United States Administration could not undertake unless public opinion was read to support it.
2. In conversation with His Majesty's Ambassador at Washington on 17th September President Roosevelt stated that he intended to maintain United States troops and ships in the Far East and hoped that the French and ourselves would be able to do the same. There was a difference, he felt, between Tientsin and Shanghai; the latter was a vital place. If the British and French had to leave Tientsin it should be as a result of this recognizable military pressure and not as the outcome of a diplomatic agreement which could be represented as 'appeasement' or leaving the United States in the lurch.
3. Such an agreement might make it difficult for him to avoid having to vacate China with French and ourselves.
4. The President clearly wanted to resist and thought that joint resistance at Shanghai would be much easier if public opinion was roused by Japanese aggression; also that if we stood together the Japanese would not go to war.
5. The United States support is felt by the Ambassador to depend upon the state of public opinion at the time.