The San Francisco 49ers have an option to own 100% of Leeds United and Elland Road by January 2024, BBC Radio Leeds understands.
The investment arm of the NFL franchise, 49ers Enterprises, increased their stake in Leeds to 44% in November.
The deal to take total ownership could be worth in excess of £500m.
Chairman Andrea Radrizzani remains the majority shareholder and his company Aser has the option to void the deal.
However, it is expected the 49ers will take control before January 2024 - though if the option was not activated both parties could continue working together as they have done since the 49ers initially bought a 10% share of the club in 2018.
Radrizzani bought a 50% stake in Leeds in January 2017, before taking 100% control by buying the remaining shares from former co-owner Massimo Cellino in May that year.
He bought Elland Road in June 2017 via his Singapaore-based company Greenfield Investment, 13 years after the club were forced to sell it to reduce debts following relegation from the top flight.
Any future deal would depend on various factors, including future spending and the club's league status.
Leeds are currently 14th in the Premier League after 15 games, having finished ninth last season in their first season back in the top flight since 2003-04.
Leeds vice-chairman Paraag Marathe, president of 49ers Enterprises, told BBC Sport in May that fans should "trust the intentions" of the club's American investors following the involvement of three US-owned Premier League teams in the failed European Super League.
He said the 49ers' plans were "pure" and promised to make Leeds "one of the biggest clubs in the world".
He added they plan to keep Elland Road, but modernise and increase the capacity of the stadium.
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