Imports from China to the U.S. have cost Americans millions of manufacturing jobs. But building a trade wall around America — as President-elect Donald Trump proposes — will hurt American consumers and U.

The move was the latest escalation in the back and forth between Beijing and Washington over products considered vital to national security.

Beijing announced export controls on 28 defense-focused U.S. companies ahead of President-elect Donald Trump taking office.

China's Ministry of Commerce adds 28 U.S. entities to export control list to "safeguard national security and interests."

The companies have found plenty of new channels to the U.S. market — demonstrating the potential limits of the tariffs Donald Trump has promised to impose.