52 Lord Cranborne, U.K. Secretary of State for Dominion Affairs, to Commonwealth Government
Circular cablegram M273 LONDON, 28 August 1941, 9.12 p.m.
IMMEDIATE MOST SECRET
My circular M.268 of August 27th.  We have now given further consideration to question of action which it would be appropriate for us to take in respect of Japan to reinforce the warning which has been delivered to that country by the United States Government.
In his broadcast of 24th August, the Prime Minister  made it clear that we should range ourselves at the side of the United States if the latter became involved in war with Japan, but we feel that it is desirable to warn the Japanese Government on our own part and directly that, apart from our support of United States, we should be compelled in the interests of security of our own territories to take counter measures in the event of further Japanese expansion.
We should prefer to link our own warning specifically with that given by United States, but this we feel would require the concurrence of the latter. We should also prefer to adhere to the wording elaborated at the Prime Minister's recent meeting with President Roosevelt unless United States Government see serious objections.
In these circumstances, His Majesty's Minister at Washington  has been instructed to inform United States Government that we should propose to request His Majesty's Ambassador at Tokyo  to address the Japanese Government in terms of formula (1) contained in my immediately following telegram. If United States Government on other hand would prefer that we did not specifically mention the warning conveyed to Japan by them, we should propose that our communication should follow terms of formula (2), text of which is also contained in my immediately following telegram. 
In either case, it is proposed that the communication should be made orally though an Aide Memoire of what is said might be communicated to Japanese authorities.
We are making it clear to the United States Government that our communication would be subject to the concurrence of His Majesty's Governments in the Dominions. We hope that the Dominion Governments would agree in principle with the line which we propose to take and would also be prepared to make similar communications to Japanese Government or authorize us to do so on their behalf.
We will telegraph further as soon as we receive reply from His Majesty's Minister at Washington as to the United States Government's attitude. In the meantime we shall be grateful to learn whether you concur generally in the action proposed.