New York Times columnist Thomas Friedman wrote on Tuesday that after visiting the U.S.-Mexico border he believes the solution for the immigration crisis is a “high wall.”

“The whole day left me more certain than ever that we have a real immigration crisis and that the solution is a high wall with a big gate — but a smart gate,” Friedman wrote.

Friedman echoed those sentiments while appearing on CNN Wednesday night when pressed by Wolf Blitzer.

“Wolf, I’m as radically pro-immigration as they come,” Friedman said. “But it’s pretty clear to me that unless we can assure a significant number of Americans that we can control our border, we’re never going to have the proper immigration flow I think we need, we desire, and that we have actually a moral responsibility — given our history as a nation of immigrants, and a refuge for people fleeing persecution.”

“We have a president who actually, when you think about it, Wolf, he has the chops with his base,” Friedman continued. “If he were to sit down, call Nancy Pelosi up, say, ‘We’re going up to Camp David. You bring your immigration team, I’ll bring mine. I’ll leave Stephen Miller at home, and we will actually sort out a compromise here.’ … Democrats were ready to fund more border security, but at the same time we’re going to create a legal pathway for people here, limits the number of ICE arrests and we’re going to have a rational inflow of people.”

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Immigration and the southern border are likely to be key issues President Donald Trump campaigns on in 2020. He has tweeted about the subjects multiple times in recent days.

“Can anyone comprehend what a GREAT job Border Patrol and Law Enforcement is doing on our Southern Border,” Trump tweeted. “So far this year they have APPREHENDED 418,000 plus illegal immigrants, way up from last year. Mexico is doing very little for us. DEMS IN CONGRESS MUST ACT NOW!”

“Mexico’s Soldiers recently pulled guns on our National Guard Soldiers, probably as a diversionary tactic for drug smugglers on the Border,” Trump tweeted. “Better not happen again! We are now sending ARMED SOLDIERS to the Border. Mexico is not doing nearly enough in apprehending & returning!”

“A very big Caravan of over 20,000 people started up through Mexico,” Trump tweeted. “It has been reduced in size by Mexico but is still coming. Mexico must apprehend the remainder or we will be forced to close that section of the Border & call up the Military. The Coyotes & Cartels have weapons!”

“The American people deserve to know who is in this Country,” Trump tweeted. “Yesterday, the Supreme Court took up the Census Citizenship question, a really big deal. MAKE AMERICA GREAT AGAIN!”

This week, Trump signed a “memorandum ordering the secretary of state and the secretary of homeland security to submit plans within four months to crack down on overstays, such as punishing countries whose citizens have high rates of overstays and requiring foreign travelers to post ‘admission bonds’ that would be repaid once they leave the country.”