One of Donald Trump’s top advisers says the Republican nominee’s plan to block travel from any country affected by terrorism is not workable.

In an interview on NPR’s “Morning Edition,” Retired Army Lt. Gen. Michael Flynn said he would love to hear if whether the travel ban was workable during the debates.

“To put a blanket [ban] on any organization, any segment of the population, is not workable, but we do have to recognize what types of things must we be able to do to continue to protect our own country and our way of life,” he said.

Flynn’s name was floated as a potential vice presidential pick for Trump before Trump picked Indiana Gov. Mike Pence. Flynn also spoke at last month’s Republican National Convention.

In a radio interview, Pence hinted the ban would also include Christians and Jews. Trump previously called for a blanket ban on just Muslims.