"The United States calls on all allies and partners to vote against negotiations on a nuclear weapons treaty ban, not to merely abstain. In addition, if negotiations do commence, we ask allies and partners to refrain from joining them," a letter obtained by the Kyodo news agency on Tuesday said.
The letter is said to be dated October 17.
According to the news agency, in case of enforcement of the nuclear weapons ban treaty, it could have a "direct impact" on the US capability to implement its commitments on the NATO and Pacific deterrence, as well as on the US partners' and allies' possibilities to participate in joint operations with nuclear-weapon states.
Earlier in October, a draft UN resolution on launching negotiations on nuclear weapons ban was introduced by delegations from Australia and other non-nuclear-weapon states.
According to Kyodo, over 50 states expressed support for the initiative by the end of the previous week.
The draft resolution is expected to be submitted for confirmation this week in order to be considered by the General Assembly at the plenary meeting in December.