President Donald Trump is expected to sign an executive order on Wednesday that will begin the construction of a U.S.–Mexico border wall, making good on one of his most infamous campaign promises.

Trump made the announcement himself in a tweet late on Tuesday night following reports of the impending order:

Big day planned on NATIONAL SECURITY tomorrow. Among many other things, we will build the wall! — Donald J. Trump (@realDonaldTrump) January 25, 2017

The executive order is expected to set out federal funding to pay for the wall and comes as part of a wider national security drive that focuses heavily on immigration.

The use of federal funding to construct the wall has been criticized as Trump falling back on his promise that Mexico would pay for the wall. As president-elect, he stated that the U.S. would fund the wall’s construction, which would be repaid by Mexico. Mexican President Enrique Peña Nieto has repeatedly said his country would not pay for the wall.

Aides and experts that have briefed on the draft orders reported to Reuters that Trump plans to implement a temporary ban on refugees arriving to the U.S. from the Middle East as well as visa suspension for Syrians and citizens from a number of other Eastern and African countries.

Both issues were among the most contentious pledges at the forefront of Trump’s electoral drive—the building of a border wall to the south and his “total and complete shutdown” on Muslim immigrants.

It’s possible that there are several other controversial ideas on the agenda. The New York Times reports that the administration will look at reviewing whether to resume the CIA’s notorious “black-site” secret prison program, keep Guantánamo Bay detention center open, and to declare the Muslim Brotherhood a terrorist organization.

During his first week in office, the president has already made thorough use of executive orders, bypassing Congress, to very publicly illustrate his commitment to campaign trail promises and his voters.

Within just a few days, he has reinstated the global gag rule on abortion, withdrawn from the TPP trade deal, and revived construction approval for the two controversial oil pipelines.

H/T New York Times