WASHINGTON (Reuters) - U.S. President Donald Trump on Thursday said his concept of a wall along the U.S. border with Mexico “has never changed or evolved,” contradicting comments made by his chief of staff.

White House chief of staff John Kelly told Hispanic lawmakers during a Wednesday meeting that some of Trump’s immigration views during the campaign were “uninformed,” according to reports in the Washington Post and New York Times.

Kelly, in an interview later with Fox News, said the Republican president’s views have evolved.

In an apparent rebuke of Kelly, Trump tweeted on Thursday: “The Wall is the Wall, it has never changed or evolved from the first day I conceived of it.”

The border wall stands at the center of a congressional struggle to overhaul immigration before the March expiration of a program protecting so-called “Dreamers” - immigrants who were brought to the country illegally as children.

Trump wants any deal to include funding for the wall, which Democrats oppose and is expected to cost more than $20 billion.

During the campaign, Trump supporters cheered when he loudly promised a barrier along the 2,000-mile (3,200-km) U.S.-Mexico frontier to keep out drug smugglers and undocumented immigrants and have Mexico pay for it. Since taking office, he has acknowledged there are geographical barriers such as mountains and rivers along the border where a wall would not be necessary.

“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.,” Trump said on Twitter on Thursday.

Talks have fallen apart following Trump’s reported derogatory comments at a White House meeting last week targeting immigrants from Haiti and African nations as being from “shithole” countries, remarks that drew international condemnation.

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Trump, who has denied using that word, on Wednesday declined to say to Reuters what specific words he used.

The Congressional Black Caucus and other Democratic lawmakers said on Thursday they were introducing a resolution of disapproval in the House of Representatives to condemn Trump’s remarks.

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“The last part of the resolution is to ask that the president retract his words and issue an apology,” Representative Cedric Richmond, who chairs the caucus, told reporters.

Jerrold Nadler, the top Democrat on the House Judiciary Committee, said more than 130 House members had signed on to the censure resolution. But it is up to Republican House Speaker Paul Ryan whether to bring it up for a vote.

Kelly told Fox News on Wednesday the administration was considering visa fees and a renegotiation of the North American Free Trade Agreement to secure revenue from Mexico.

In an interview with Reuters on Wednesday, Trump said he was considering terminating NAFTA.

Mexico, in response to Trump’s tweets on Thursday, reiterated that it would not fund the wall’s construction.

“Mexico will not negotiate NAFTA, nor any other aspect of the bilateral relationship, through social networks or the media,” its foreign ministry said in a statement.