"In a non-deal scenario without another delay of US tariffs, I see the EU going for a tit-for-tat approach, ie imposing 30% tariffs on selected US goods, not yet all goods, like the well-known motorcycles, cars, clothing and alcohol," he said in emailed comments.

LONDON—President Trump and European Commission President Ursula von der Leyen are scheduled to meet Sunday during the U.S. president’s visit to Scotland, raising hopes that the U.S. and Europe are close to a trade deal that would avoid a trans-Atlantic trade war.

Still, investors have been bracing for increased volatility heading into August 1, which the U.S. has set as a deadline for raising levies on a broad swath of trading partners.