517 Lord Cranborne, U.K. Secretary of State for Dominion Affairs, to Mr R. G. Menzies, Prime Minister
Circular cablegram M120 LONDON, 23 June 1941, 10.25 p.m.
FOLLOWING FOR THE PRIME MINISTER MOST SECRET
My Circulars M. 114 and M. 115. 
In support of anything which H.M. Ambassador at Tokyo  may say regarding the effect on us of a Japanese attack on the Netherlands East Indies, the United States Ambassador  has been authorized by his Government to speak to the Minister for Foreign Affairs  in the sense that, as the United States are doing their utmost generally to keep Britain supplied across the Atlantic, they obviously could not stand by and watch Britain's lifeline being cut in the Pacific through an attack on Singapore or the Netherlands East Indies.
H.M. Ambassador and the United States Ambassador have agreed to act only if the situation again deteriorates or Matsuoka provides an opening that should not be missed.