President Donald Trump's former top economic advisor says the trade war with China is unwinnable and is hurting the U.S. economy.

Gary Cohn told the BBC in an interview that aired Thursday that tariffs were raising the cost of importing much needed products from China and were in fact neutralizing Washington's plan to stimulate growth through tax cuts.

"When you build plant equipment, you're buying steel, you're buying aluminium, you're buying imported products and then we put tariffs on those, so literally the tax incentive we gave you with one hand was taken away with the other hand," said Cohn.

Cohn, the former director of the U.S. National Economic Council, announced his resignation in April 2018 after Trump decided to impose import tariffs on steel and aluminium.

In the BBC interview, he described himself as openly anti-tariffs before adding that "everyone loses in a trade war."

The former Goldman Sachs president said Trump's plan to force Beijing's hand on trade imbalances via tariffs was a view that the president had held "forever" but were in fact offering Chinese bureaucrats a convenient excuse.

WATCH: Gary Cohn on America's competitive advantage, January 2019