The 10-hour daily flights would connect United's Washington Dulles hub with Moscow's Domodedovo Airport, the airline said in a statement.
The new route is expected to serve as an important cargo entryway for Russia's growing demand for industrial and consumer commodities, United executive vice president John Tague said.
United will offer a similar direct flight to Dubai.
"Commerce and tourism are growing exponentially in both Dubai and Moscow, and many of our cargo and corporate customers are traveling and shipping there more often to capitalize upon the economic health in these regions," Tague said.
Mail also is expected to represent a significant amount of cargo volume on the flights.
The plans still require government approval.
Domodedovo Airport spokeswoman Yevgenia Bekmambetova confirmed Wednesday that negotiations were under way with United.
United Airlines would be the third U.S. carrier to offer direct flights after Delta Air Lines, which offers daily flights to New York and Atlanta, and American Airlines, which plans to launch a Chicago-Moscow flight on June 2.
United would compete directly with Aeroflot, which operates nonstop flights between Moscow and Washington on Saturdays.
It was unclear how United's daily return flights from Moscow to Washington would garner enough passenger traffic. Aeroflot's once-a-week flight from Moscow to Washington is rarely full, an Aeroflot representative said. She spoke on condition of anonymity, saying she was not authorized to speak with the media.
United Airlines said its trump card would be Boeing 767 jets flying in combined passenger and cargo mode between Washington and Moscow. The Boeing 767s would be configured with 10 first-class seats, 32 business-class seats and 141 economy seats, the airline said.
Delta and Aeroflot offer two-class cabins.
American Airlines and United say they are looking to Russia to capitalize on the country's fast-growing economy.
A total of 172,000 people came to Russia from United States last year, of which 38,000 were tourists, said Irina Tyurina, spokeswoman for the Russian Union of Travel Agencies. The number of Russian tourists visiting the United States was 32,800 last year, she said.
United's flights would leave Washington at 4:45 p.m. and arrive in Moscow at 9:30 a.m. the next day. The return flights would leave Moscow at 11:20 a.m. and arrive in Washington at 3:35 p.m.
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