The United States and European Union have reached a trade deal, ending a months-long standoff between two of the world's key economic partners.

After make-or-break negotiations between President Donald Trump and European Commission President Ursula Von der Leyen in Scotland, the pair agreed on a blanket US tariff on all EU goods of 15%. That is half the 30% import tax rate Trump had threatened to implement starting on Friday.

Trump said the 27-member bloc would open its markets to US exporters with zero per cent tariffs on certain products.

Von der Leyen also hailed the deal, saying it would bring stability for both allies, who together account for almost a third of global trade.

Trump has threatened tariffs against major US trade partners in a bid to reorder the global economy and trim the American trade deficit.