Please give the following message to the Prime Minister [1] for
his most secret and personal information. BEGINS.

1. We have had in mind for some time that it would be desirable to
persuade the United States Government that one of the most
effective methods of checking Japanese southward movement would be
a joint declaration by the United States and ourselves that an
attack on the Netherlands East Indies or on British possessions in
the Far East would be regarded as a casus belli by both the United
States and ourselves. We have however up to now considered such a
declaration outside the range of practical politics in the United
States, and the President's [2] views as reported in my message
under reference, together with private soundings made by H.M.

Ambassador, Washington [3], tended to confirm this view.

2. The Netherlands Government recently communicated to the
Secretary of State for Foreign Affairs here [4] a memorandum [5]
suggesting that the United States Government should be approached
with a view to their making clear to Japan through diplomatic
channels that the United States could not tolerate continued
Japanese southward aggression. The Netherlands Government also
suggested that the United States Government should be informed
that they themselves and the United Kingdom Government would be
prepared, if the United States Government so wished, to make
corresponding and simultaneous declarations to the Japanese
Government. The Netherlands Government's suggestion was that these
steps should not be made public for the present and in no case
without previous consultation.

3. In the course of a discussion on another subject on the 5th
March H.M. Ambassador at Washington mentioned to Mr. Hull [6] on a
purely personal basis the possibility of a joint declaration by
the United States, the Dutch and ourselves. Mr. Hull rather
unexpectedly indicated in reply the readiness of the United States
Government to do something on these lines not involving an
unqualified threat. Lord Halifax feels that Mr. Hull's reply
should not necessarily be taken as committing the United States
Government to a joint declaration but has asked for instructions
as to the manner in which he should return to the subject. [7]

4. Matter is at present under consideration here. ENDS. [8]