A bilateral trade deal between South Korea and the US will be signed in Washington on Saturday, meeting the deadline to fast-track through the US Congress, after the two countries agreed on last-minute tweaks to the accord.

With bilateral trade exceeding $70bn a year, the pact will be Washington’s largest since the North American Free Trade Agreement more than a decade ago. But parts of the deal, agreed in April, had to be hurriedly renegotiated to meet Washington’s new guidelines on labour rights and the environment.