A top aide to Donald Trump insisted on Sunday that the administration is prepared to shut down the government in order to get the funding it demands to build a long-promised wall on the US-Mexico border.

Democrats, in response, flatly refused to shift position in order to help avoid such a government freeze.

Stephen Miller, senior adviser to the White House and a key, controversial aide to the president seen as instrumental in forging a hardline immigration policy, said on Sunday: “We’re going to do whatever is necessary to build the border wall.”

He told the CBS political talk show Face the Nation on Sunday morning that such a barrier was necessary to prevent “this ongoing crisis of illegal immigration” – his characterization of migrants from Mexico, central and south America attempting to enter the United States without authorization, typically to escape poverty or seek shelter from violence in their country of origin, or both.

The Trump administration is attempting to obtain necessary support from Democrats in Congress for substantial federal funding to build the wall and must pass the measure as part of a wider budget by the end of Friday, or trigger a temporary shutdown of vital government business.

Asked on CBS if “whatever is necessary” included a government shutdown, Miller said it did.

“If it comes to it, absolutely,” he said.