Apple (AAPL - Get Report) shares took a hit Friday after President Trump threatened U.S. companies that rely on China for manufacturing. 

Shares of the iPhone giant fell 4.6% after Trump tweeted in the late morning on Friday that U.S. companies are "hereby ordered to immediately start looking for an alternative to China." China serves as Apple's manufacturing base as well as its third-largest consumer market by revenue, behind the U.S. and Europe. 

Although the President does not have the authority to order companies to adjust their supply chains, Trump's statement added another level of uncertainty to the ongoing U.S.- China trade conflict. He added that companies should begin "making their products in the USA." 

Following Trump's tweets, Apple as well as chip stocks, many of which have significant exposure to China, took a substantial hit amid a broader market selloff. The SOX semiconductor index was down 4% Friday while the Dow Jones fell 2.1%. 

Apple is already working "aggressively" to shift iPhone production out of China, wrote Wedbush analyst Dan Ives in a note Friday -- but it'll be a lengthy process. 

"On the supply chain, we believe Apple is aggressively looking at alternative options within the supply chain in light of this US/China UFC trade battle around moving 5%-7% of iPhone production to India and/or Vietnam, away from China, which would in a best case scenario be ready to roll 18 months from now in our opinion," he said. 

It would take more than five years to move 50% of iPhone production away from its core Foxconn base in China, he estimated, and more than three years to move 30%. In the meantime, the trade turmoil between the U.S. and China represents an overhang of between $20 and $25 on Apple shares, according to Ives. Shares of Apple were recently trading at just above $202.

Year to date, Apple's stock is up 34%. 

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