The US Department of State has urged UK construction companies to build strategic alliances with US firms to help boost their chances of winning a $500m deal.
US practice Kieran Timberlake has won a competition to design the new $1bn (£648m) US Embassy in London. The construction contract is also expected to be given to a US-based firm for security reasons.
The US Bureau of Overseas Buildings Operations acting director Adam Namm said non-US companies may be employed as subcontractors by the prime contractor subject to approval by the US Government.
Aecom, Bechtel, Jacobs, Bovis Lend Lease and Parsons Brinckerhoff are among the US firms likely to win if a construction management route is chosen.
Texas-based Zachry or Alabama-based Caddell, which have built US Embassies previously are other contenders for the project if a traditional contracting route is chosen.
The main construction work will begin in 2013 and is scheduled to be complete in 2017.