Whilst the Germans sought to blockade Britain, the British were seeking to blockade the whole of occupied Europe. The Vichy Government in France had appealed to the United States to be allowed to import food, as they faced growing shortages due to German requisitioning. Churchill made a typically robust argument in a telegram sent to the United States on 3rd March 1941:
Neither the Vichy Government nor its agents in North Africa show any spark of nobility or courage or any active will to resist. They may hope for our victory but will do nothing to help, since if we lose they may thus, they trust, have acquired merit in German eyes, while if we win they assume we shall in any event restore France. Meanwhile, they expect us to allow them to be amply supplied from overseas.
7. The reasons why the supply of foodstuffs to unoccupied France would damage our blockade are explained in the following paragraphs.
8. Factories in unoccupied France are working more and more for the Germans, and we naturally become less and less inclined to help feed the workers who make the bombs that fall on our cities. Any supplies sent from overseas help to relieve Germany of the burden of feeding those thus employed.
From a telegram sent by Churchill to Lord Halifax, British Ambassador to the United States, see TNA CAB 66/15/21