FILE PHOTO: U.S. President Donald Trump looks up while hosting a House and Senate leadership lunch at the White House in Washington, U.S. March 1, 2017. REUTERS/Kevin Lamarque/File Photo

WASHINGTON (Reuters) - President Donald Trump said on Sunday he expected Mexico to pay for the wall he has promised to build along the southern border, resuscitating a campaign promise that roiled U.S. relations with Mexico in the first week of his presidency.

“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,” Trump said in a Twitter post.

Trump returned to his Mexico demand on a morning in which he simultaneously tried to pressure congressional Democrats to include funding for the border wall in must-pass spending legislation needed to keep the U.S. government open beyond Friday.

A spokesman for the Mexican president’s office said President Enrique Pena Nieto has repeated that Mexico will not pay for the wall.

The Republican president’s demand that Mexico pay for the border wall triggered a diplomatic crisis with the southern U.S. neighbor during the first week of his presidency. Pena Nieto on Jan. 26 scrapped a planned trip to meet with Trump and the White House floated the idea of a 20 percent tax on goods from Mexico to pay for the wall.

The two leaders agreed the following day not to talk publicly about payment for the wall, the Mexican government said. The White House said the two recognized they had differences over the proposed wall but agreed to “work these differences out.”

Trump sought the wall, projected to cost more than $20 billion, as part of his effort to curb illegal immigration. Mexico has rejected payment for the construction project as out of the question.

Attorney General Jeff Sessions told ABC’s “This Week” on Sunday the wall would get paid for one way or another.

“I don’t expect the Mexican government to appropriate money for it but there are ways that we can deal with our trade situation to create the revenue to pay for it, no doubt about it,” Sessions said.