(Reuters) -U.S. tech heavyweights, banks and oil majors fell sharply on Friday after China retaliated to Trump's tariffs with steep duties, amplifying worries of a global economic downturn.

China slapped additional duties of 34% on U.S. goods, set to go into effect April 10. It also announced curbs on exports of some rare-earths and added several U.S. firms to its export control list and the "unreliable entities" list, which allows Beijing to take punitive action.

U.S. President Donald Trump on Wednesday announced 34% duties on imports from China along with a 10% baseline tariff on most goods flowing into the U.S., triggering a massive market meltdown on Thursday.

Investors are already fretting over potential supply chain disruptions, price hikes and demand destruction for everything from cars and smartphones to sneakers.

Shares of Tesla and Apple - among companies with a large exposure to China - were down 8% and 4%, respectively. While both companies have local production in China, duties on U.S.-imported parts could squeeze margins and force them to raise prices.

"Several tech companies have established local supply chains in China. Most source components from China already, and hence, disruptions should be controllable, though we do expect price hikes on parts and components not being sourced from China," said Nishant Udupa, practice director at research firm Everest Group.

For Tesla, already in a bruising price war with local Chinese rivals, raising prices would pressure demand even further.

"Apple's smartphone sales had already been declining in China for some time, faced with growing, cheaper competition. So, the prospect of steep import duties being imposed is likely to sharply erode sales even further," said Susannah Streeter, head of money and markets, Hargreaves Lansdown.

Shares of other Big Tech firms, including Alphabet, Microsoft and Meta, which have limited exposure to China, fell between 2% and 4%.

"Big Tech stocks did not prove immune to growth worries in 2022 and they are struggling again now for the same reason, and from even higher starting point in terms of valuation this time around," said Russ Mould, investment director at AJ Bell.

Crude prices, already under pressure from an expected OPEC+ oil output hike in May, added to the losses.[O/R]

Oil majors Exxon fell 3.5% and Chevron declined 4.1%. Top oilfield service company SLB dropped 5.7%, and the biggest U.S. refiner by volume, Marathon Petroleum, fell 5.8%. Chemicals company DuPont slid 11%.

"The trade war escalated, recession fears rise and consequently oil demand growth is to take a sizeable hit," said Tamas Varga, analyst at PVM.