The treaty, the first of its kind, is intended to ease exports of weapons between the two countries by reducing the need for export licenses and other U.S. government approvals.

The treaty creates “approved communities” of government agencies and companies that may export and transfer certain U.S. items to pre-approved buyers within the United States and United Kingdom and to locations where military operations are being conducted or supported, according to the State Department.

So far, only 10 British companies have signed up, but London is trying to increase the number by publicizing the treaty more, said Tracy Buckingham, assistant director for North America and Northern Europe at the British trade agency.

Britain accounts for 70% of global defense exports to the United States, and British companies have significant roles on big U.S. weapons programs like the F-35 Joint Strike Fighter built by Lockheed Martin and the M777 Howitzer.