On Friday, President Donald Trump said “some of” his predecessors supported his idea to fund the construction of a wall on the U.S. southern border, although four living former presidents have since denied this claim.

“This should have been done by all of the presidents that preceded me,” Trump said Friday at a press conference about building a barrier. “And they all know it. Some of them have told me that we should have done it.”

On Monday, 94-year-old Jimmy Carter — the oldest living ex-president — said he and Trump never had a conversation about this subject.

“I have not discussed the border wall with President Trump, and do not support him on the issue,” Carter said in a statement tweeted by The Carter Center.

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Angel Urena, a spokesman for Bill Clintonsaid the former Democratic president “never said that” and added Clinton and Trump haven’t spoken since the latter’s inauguration.

Freddy Ford, a spokesman for George W. Bushsaid in an interview with CNN that Bush and Trump “haven’t discussed this.”

A spokesperson for Barack Obama did not directly respond to Trump’s claim, although he cited a powerful remark Obama made in a speech to the assembled representatives of the United Nations’ member states in September 2016.

“A nation ringed by walls would only imprison itself,” Obama said at the time.

Trump’s immediate predecessor also slammed the notion of the wall during a commencement address at Rutgers University in May 2016, saying the idea ran contrary to the U.S.’s fundamental status as a “melting pot” of immigrants.

Trump’s insistence on funding a border wall to prevent illegal immigration has caused a government shutdown, which entered its 18th day on Tuesday. Democrats, who hold the majority in the House of Representatives, have repeatedly said they refuse to provide funds for the barrier.