Trump says the border wall 'has never changed or evolved,' contradicting Chief of Staff John Kelly

President Trump tweeted early Thursday that his border wall “has never changed or evolved,” following White House Chief of Staff John Kelly's suggestion the president’s attitude toward his paramount campaign promise had “changed.” 

“The Wall is the Wall, it has never changed or evolved from the first day I conceived of it. Parts will be, of necessity, see through and it was never intended to be built in areas where there is natural protection such as mountains, wastelands or tough rivers or water,” Trump tweeted.

But on Wednesday, Kelly told Fox News that the president had “changed” his view.

“This president, if you see what he has done, he has changed the way he has looked at a number of things,” Kelly said in exclusive interview on “Special Report” Wednesday. “He’s very definitely changed his attitude toward DACA and even the wall.”

He added: "“Campaign to governing are two different things, and this president has been very, very flexible in terms of what is within the realm of the possible.”

During the interview, Kelly was pressed over comments The Washington Post said he made to Democrats, suggesting Trump "wasn't fully informed" when he promised to make a wall that stretched across the entire U.S.-Mexico border. 

"There's been an evolutionary process that this president has gone through... and I pointed out to all the members that were in the room that they all say things during the course of campaigns that may or may not be fully informed,” Kelly said.

JOHN KELLY SUGGESTS TRUMP WASN'T 'FULLY INFORMED' WHEN HE PROMISED WALL ACROSS ENTIRE BORDER

The president tweeted again, moments later, promising that the wall will be paid for by Mexico—as he vowed throughout his 2016 presidential campaign.

“The Wall will be paid for, directly or indirectly, or through longer term reimbursement, by Mexico, which has a ridiculous $71 billion dollar trade surplus with the U.S. The $20 billion dollar Wall is ‘peanuts’ compared to what Mexico makes from the U.S. NAFTA is a bad joke!” he said.

Trump pointed to the North American Free Trade Agreement (NAFTA), a trade deal dating back to the Clinton administration between the U.S., Canada, and Mexico. Trump has repeatedly called NAFTA “the worst trade deal in the history of this country.”

CANADA, MEXICO VOW TO FIGHT TRUMP IF HE PULLS OUT OF NAFTA 

The president said this month that he promised to terminate the agreement if the U.S. couldn’t secure a better deal. But the administration’s aggressive talk on the deal set off concern in Mexico and Canada, with those nation’s leaders warning Trump. Mexican officials have warned they’ll leave the negotiating table if the president decides to trigger the six-month withdrawal process from the deal.

Congressional Republicans from U.S. border states whose economies depend on trade have urged the administration to modernize the deal, rather than to pull out. The next round of NAFTA talks are expected on January 23 in Montreal.

The president’s tweets also come as Republicans and Democrats are battling on Capitol Hill to keep the government running, as the current temporary spending bill expires Friday night at 11:59:59 p.m. EST. The president is pushing for his wall along the U.S.-Mexico border and, like all Republicans, for increased defense spending, while the Democrats are fighting to keep the Obama-era Deferred Action on Childhood Arrivals program, which shields more than 700,000 immigrants who were brought to the U.S. illegally as children from immigration.

The president doubled down on the need for the wall later Thursday morning, warning Congress that without it, there would be "no deal."

"We need the Wall for the safety and security of our country. We need the Wall to help stop the massive inflow of drugs from Mexico, now rated the number one most dangerous country in the world. If there is no Wall, there is no Deal!"

Fox News’ Kristin Brown, Alex Pappas, and Kevin Corke contributed to this report. 

Brooke Singman is a Politics Reporter for Fox News. Follow her on Twitter at @brookefoxnews.