Commissioners at the Federal Maritime Commission (FMC) voted four to one in favour of the 10-year pact, which will see the two companies run 185 ships in Asia-Europe, transatlantic and transpacific trades.
FMC decided not to seek further information about 2M's impact on shippers and ports.
US approval will come into force on Saturday, commissioner Richard Lidinisky told Reuters.
It was thought Maersk still needed clearance from Europe and China, but the shipowner said on Thursday: “The US was the only remaining jurisdiction where the parties had to obtain formal approval.
