President Donald Trump appeared to push back Thursday against comments by his chief of staff that his thinking on the long-promised border wall had "evolved," with the president insisting that his views on the barrier hadn't changed.

"The Wall is the Wall, it has never changed or evolved from the first day I conceived of it," Trump said in the first of two tweets. "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, nevertheless, suggested Mexico won’t be paying for the wall as quickly as he said it would during the campaign, saying that America’s southern neighbor might fund the barrier "indirectly" and over a long period of time.

"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.," he tweeted. "The $20 billion dollar Wall is ‘peanuts’ compared to what Mexico makes from the U.S. NAFTA is a bad joke!"

Moments later he tweeted that there would be no broader immigration deal with Congress "if there is no Wall."

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"We need the Wall for the safety and security of our country," he wrote. "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!"

The tweets came less than 24 hours after White House Chief of Staff John Kelly reportedly indicated that his boss's views on the wall — one of Trump's signature campaign promises — had evolved and that Trump hadn’t been "fully informed" when making the key campaign vow.

"I told them, there has been an evolutionary process that this president has gone through," Kelly said during an interview with Fox News on Wednesday night, recounting his meeting earlier in the day with the Congressional Hispanic Caucus. "I pointed out to all of the members, that they (candidates) say things over course of campaigns that may or may not be fully informed."

Trump, Kelly added, "changed the ways he’s looked at a number of things" — including the wall.

"He has evolved in the way he's looked at things. Campaigns and governing are two different things," Kelly added. "And this president has been very flexible in terms of what is within the realm of the possible."

Kelly added that the administration has some ideas to fund the wall, which include "things like visa fees, renegotiation on NAFTA."

"In one way or another, it's possible that we could get revenue for Mexico but not directly from (their) government," he said.

Trump had repeatedly promised during his campaign, and over the course of his first year in office, that the U.S. would build a massive border wall and that Mexico would pay for it.

Yet, the White House is engaged in negotiations with Congress over a broader immigration deal that could involve the U.S. funding parts of the wall, as well as extending protections for recipients of DACA, the Deferred Action for Childhood Arrivals program.