U.S. officials say Secretary of State John Kerry will sign a landmark treaty regulating the $70 billion global conventional-weapons trade during the annual UN General Assembly meeting this week.
The officials, speaking on condition of anonymity, said Kerry will sign the treaty on September 25.
The move would put President Barack Obama's administration at odds with the powerful U.S. gun lobby and some lawmakers who oppose it.
The United States is the world's largest arms exporter, and its accession is seen as critical to the treaty's success.
The treaty, adopted by the UN General Assembly in April, has been signed by 86 countries, but many major exporters of conventional weapons, including Russia and China, have not signed on.
U.S. accession to the treaty would require ratification by the Senate.
Based on reporting by Reuters and AP