Toyota Motor Corp. said Tuesday that U.S. President Donald Trump's proposal to slap tariffs on Mexican-made goods could cost its major suppliers $1 billion, highlighting growing concern in the U.S. auto sector about the potential damage of a new front in the Trump administration's trade wars.

Trump has said he will apply tariffs of 5 percent on Mexican goods next Monday if Mexico does not halt the flow of illegal immigration, largely from Central America, across the U.S.-Mexican border. Those tariffs would gradually rise to 25 percent by Oct. 1 if Mexico does not satisfy Trump's demands.

Faced with this threat, major automakers are also planning to delay some vehicle shipments from Mexico, people briefed on the plans said Tuesday.