President Trump's steel tariff could cost Ford and General Motors $1 billion a year.

That's the hit each company could take if the tariff translates into a similar increase in steel prices, according to a Goldman Sachs (GS) analysis. Trump has proposed a 25% tariff on imported steel, along with a 10% tariff on aluminum.

$1 billion represents 12% of Ford's profit last year and 7% of GM's, the analysis said.

The report looked at Ford (F) and GM's (GM) 2017 production mix to make its calculation.

Related: Here's what corporate America is saying about Trump's tariffs

Ford said in a statement that the tariffs "could result in an increase in domestic commodity prices — harming the competitiveness of American manufacturers." GM said it supports trade policies "that enable U.S. manufacturers to win and grow jobs in the U.S."

Both automakers say they use mostly American-made steel for vehicles they make in the United States.

Trump argues that the tariffs will bolster US production of steel and aluminum and combat unfair trade practices. But businesses outside the steel and aluminum industries have warned that the tariffs will lead to higher prices and hurt the economy.

Related: Trump tariffs: Another anti-business decision by the CEO president

The American International Automobile Dealers Association, which was formed to advocate free trade, said car prices could go up "substantially." The group also warned that retaliatory tariffs from other countries could drive up the price of US goods in general.

— CNN's Jackie Wattles and Matt Egan contributed to this report.