President Donald Trump says his concept of a wall along the US 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 elaborated in an interview later with Fox News, saying that the Republican president's views have "evolved".
In an apparent rebuke of Kelly, Trump wrote on Twitter on Thursday: "The Wall is the Wall, it has never changed or evolved from the first day I conceived of it."
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The border wall stands at the centre 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 $US20 billion ($A28 billion).
During the campaign, Trump supporters cheered when he loudly promised a barrier along the 3200 km US-Mexico frontier to keep out drug smugglers and undocumented immigrants and have Mexico pay for it. Since taking office, he has acknowledged there were 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 $US71 billion dollar trade surplus with the US," Trump said on Twitter on Thursday.
Kelly told Fox News in an interview on Wednesday that the administration was considering visa fees and a renegotiation of NAFTA as ways to get revenue from Mexico.
