Commerce Secretary Wilbur Ross says the president will sign a memo ordering him to determine the impact of rising aluminum imports.

High-purity aluminum is used in a number of defense applications, including military planes and the armor-plating of military vehicles.

Ross says there is only one American smelter that produces high-purity, aerospace-quality aluminum.

He says, "It's very, very dangerous, obviously from a national defense point of view, to only have one supplier of an absolutely critical material."

This is the president's second such move. He initiated an investigation into steel imports last week.

The investigation could lead to tariffs on aluminum imports.