Interior Secretary Ryan Zinke proposed Tuesday that the U.S. build its border wall on Mexico’s side of the border.

“The border is complicated, as far as building a physical wall,” Zinke said at an event held by the Public Lands Council, according to E&E News. He went on to say, “The Rio Grande, what side of the river are you going to put the wall? We’re not going to put it on our side and cede the river to Mexico. And we’re probably not going to put it in the middle of the river”

The interior secretary added that some areas along the border are too physically imposing for a wall to be necessary. The Rio Grande, however, spans 1,200 miles and President Trump has called for a wall along the entire border. Zinke’s comments are the first from a Trump administration official to suggest that the U.S. should build the wall on Mexican territory.

A Customs and Border Protection spokesman told The Daily Caller, “We are currently evaluating all options available for the construction of the Wall as directed by the Executive Order.”