The American effort soon overtook the British. British scientists who visited the United States in 1942 were astounded at the progress and momentum the Manhattan Project had assumed. On 30 July 1942, Anderson advised Churchill that: "We must face the fact that ... pioneering work ... is a dwindling asset and that, unless we capitalise it quickly, we shall be outstripped. We now have a real contribution to make to a 'merger'. Soon we shall have little or none". But Bush and Conant had already decided that British help was no longer needed. In October 1942, they convinced Roosevelt that the United States should independently develop the atomic bomb, despite the agreement of unrestricted scientific interchange between the US and Britain.