President Trump's long-promised southwest border wall shouldn't be built on the American side of the line, according to Interior Secretary Ryan Zinke.

"The border is complicated, as far as building a physical wall," Zinke told the Public Lands Council, according to E&E News. "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."

Zinke's comments highlight one of the practical difficulties that deterred construction of the border fence that Congress authorized in 2006, particularly the problem of leaving land owned by U.S. citizens on the far side of the wall. Senate Minority Leader Chuck Schumer wasted no time in highlighting his comments to buttress their case against the wall.

"These guys ... now the wall is going to be IN Mexico," Schumer spokesman Matt House tweeted.

Executive Director of American Oversight Austin Evers said that building a wall on Mexican land "raises a host of legal, procurement and long-term issues," adding that Zinke had made a compelling argument against building it at all.

"Even if Secretary Zinke is incorrect, he does raise a very serious point: Does President Trump plan to cede the Rio Grande River — a vital source of water for residents and the agriculture industry — to Mexico?" Evers said in a statement. "As the president discovered with health reform, this issue also is 'complicated.' Americans need clear answers to these difficult problems before billions of our tax dollars are spent."