United States President Donald Trump and his Attorney General insisted, on Sunday, that Mexico would fund a proposed wall on the US-Mexico border, ahead of a budget battle in which disagreement over the project threatens a government shutdown.

Trump repeated his campaign pledge of building a wall on Sunday, a project estimated to cost tens of billions of dollars.

“Eventually, but at a later date so we can get started early, Mexico will be paying, in some form, for the badly needed border wall,” he tweeted.

Attorney General Jeff Sessions also told ABC News on Sunday that “we’re going to get paid for it one way or the other” and suggested federal tax credits sent by mistake to “mostly Mexicans” could cover the cost.

Despite maintaining that Mexico will pay, Trump also blamed opposition Democrats on Sunday for blocking US funding to start construction of the wall project.

“The Democrats don’t want money from budget going to border wall despite the fact that it will stop drugs and very bad MS 13 gang members,” Trump tweeted.

US government funding expires this coming Friday, with the government currently being funded by a continuing resolution passed in December 2016.

Should Trump push for money for the wall to be included in the next round of funding, the bill is likely to get blocked by Democrats, according to House Minority Leader Nancy Pelosi.

“The Democrats do not support the wall,” Pelosi said on NBC’s “Meet the Press.”

“The Republicans have the votes in the House and the Senate and the White House to keep government open. The burden to keep it open is on the Republicans.

“The wall is, in my view, immoral, expensive, unwise.”

Despite a Republican majority in both houses, Trump needs 60 votes in the Senate to pass a spending bill, meaning he would need some Democrat support.