Japan's chief negotiator, Economic Revitalization Minister Ryosei Akazawa, had been working on a deal since April. He's made eight trips to Washington, pressing the case in person. After the deal news broke, he tweeted a photo of himself at the White House: "Mission complete. Sincere thanks to all involved."

Any agreement would likely include a 15 per cent baseline tariff on EU goods entering the US and a 50 per cent levy on European steel and aluminium, according to diplomats familiar with the talks.