The British government had believed that the United States would continue to share nuclear technology, which it considered a common discovery.  On November 9, 1945, Attlee and Canadian Prime Minister Mackenzie King traveled to Washington, D.C. to discuss future nuclear and nuclear weapons cooperation with Truman.   On November 16, 1945, a Memorandum of Intent was signed, making Canada a full partner, replacing the requirement of “mutual consent” of the Quebec Agreement before nuclear weapons were used for “pre-consultation.” There should be “full and effective cooperation in the field of nuclear energy,” but British hopes were quickly dashed, as it only concerned “fundamental scientific research.”   In the Mutual Defence Agreement, the United States and the United Kingdom undertake to “communicate or exchange with the other party the secret information, sensitive nuclear technologies and controlled nuclear information” necessary for the nuclear defence plans, delivery systems and military reactors of allies. The agreement does not provide for the transfer of actual nuclear weapons, but the exchange of enriched uranium. Article 2 of the treaty relates to the joint development of defence plans; Training of personnel on the ground and defence against nuclear weapons; the exchange of information and the assessment of hostile capabilities; The development of nuclear vector systems and the research, development and construction of military reactors.  The treaty requires the exchange of classified information on nuclear weapons when the communicating party finds, after consultation with the other party, that disclosure of this information is necessary to improve the recipient`s ability to develop and manufacture nuclear weapons.  The United States would transmit information on British nuclear weapons. In the immediate future, this would exclude information on thermonuclear weapons.  Confidential information issues are also covered by the agreement. The UK government has not published these sections “due to the need for high confidentiality and the use that such information would be intended for other potential nuclear states.
In other words, it could very well contribute to the dissemination.  The amendment of Article III to the 1958 agreement will extend this provision on December 31, 2014. The 1958 agreement strengthens overall cooperation between the United States and the United Kingdom in the area of nuclear defence; Without them, the U.S. government cannot share nuclear technology or transfer materials to the UK.