Apple shares fell 7% in Frankfurt after U.S. President Donald Trump announced sweeping tariffs on trading partners including China where the U.S. group has a big manufacturing base.

"If Apple cannot get exempted this time and assuming Apple gets hit by the accumulative 54% China tariffs and does not pass it through, we estimate about 9% negative impact to the company’s total gross margin," wrote Citi in a note.

Citi estimates Apple has more than 90% of its manufacturing in China.