United Airlines and Qatar Airways plan to end their codeshare agreement on 15 September, according to a filing with the US Department of Transportation.
The airlines have partnered since June 2007 when Qatar launched service between Newark Liberty airport and Doha, and then a month later between Washington Dulles and Doha.
United says that it continually reviews its partnerships "to ensure that they are providing both partners and our customers with added benefits".
Qatar was rumoured to be considering membership in the Star Alliance, which United is a founding member of, following the partnership with United and US Airways in 2009.
Qatar did not respond to questions by press time.