President Donald Trump reignited trade tensions ahead of the Memorial Day weekend with back-to-back social media posts targeting Apple and the European Union, sending global markets into turmoil after weeks of de-escalation provided some reprieve.

U.S. President Donald Trump cranked up his trade threats on Friday, targeting both smartphone giant Apple along with imports from the entire European Union, sending the global market roiling after wee...

The threat delivered over social media could dramatically increase the price of iPhones, potentially hurting sales and the profits of one of America’s leading technology companies.