positions of the two countries were the reverse of what they had been in 1941. American officials were concerned that Akers and other people from ICI involved in the Tube Alloys project were trying to exploit American nuclear scientific knowledge to create a profitable post-war industry. The Secretary of War, Henry L. Stimson, felt that since the United States was doing "ninety percent of the work" on the bomb, it would be "better for us to go along for the present without sharing anything more than we could help". In December 1942, Roosevelt agreed to restricting the flow of information to what Britain could use during the war, even if doing so impeded the American project. The Americans stopped sharing any information on heavy water production, the method of electromagnetic separation, the physical or chemical properties of plutonium, the details of atomic bomb design, or the facts about fast neutron reactions. This adversely impacted the work of the Montreal Laboratory, the joint British and Canadian project that was investigating nuclear reactor design. In retaliation, the British stopped sending scientists to America, slowing the pace of work there, which had relied on British scientists. The Americans then ceased all information sharing. The Tube Alloys Directorate considered whether Britain could produce a bomb without American help. A gaseous diffusion plant to produce 1 kg of weapons-grade uranium per day was estimated to cost up to £3 million in research and development, and anything up to £50 million to build in wartime Britain. A nuclear reactor to produce 1 kg of plutonium per day would have to be built in Canada. It would take up to five years to build and cost £5 million. The project would also require facilities for producing the required heavy water for the reactor costing between £5 million and £10 million, and for producing uranium metal, which would cost another £1.5 million. The project would need overwhelming priority, as it was estimated to require 20,000 workers, many of them highly skilled, 500,000 tons of steel, and 500,000 kW of electricity. Disruption to other wartime projects would be inevitable, and it was unlikely to be ready in time to affect the outcome of the war in Europe. The unanimous response was that before embarking on this, another effort should be made to obtain American co-operation. By March 1943 Bush and Conant had decided that British help would benefit some