US President Donald Trump is set to take a first step toward enacting his pledge to build a wall on the Mexican border as he rolls out a series of immigration-related decrees on Wednesday. The White House said that Trump will make the announcements in a visit to the Department of Homeland Security in the afternoon. Big day planned on NATIONAL SECURITY tomorrow. Among many other things, we will build the wall! Trump tweeted. Trump will also sign a measure targeting sanctuary cities where local officials refuse to help round up people for deportation. International media said he also plans to expand the number of customs and border agents. Stemming immigration was a central plank of Trump election campaign and his signature policy was to build a wall across the 2,000-mile (3,200-kilometer) border between the United States and Mexico. Some of the border is already fenced, but Trump says a wall is needed to stop illegal immigrants entering from Latin America. Experts have voiced doubts about whether a wall would actually stem illegal immigration, or if it is worth spending billions on a wall when there are cheaper methods, such as electronic surveillance, of achieving similar results. But a border wall has become a clarion call for the US right and far-right, the core of Trump support. Still, any action from the White House would be piecemeal, diverting only existing funds toward the project. The Republican-controlled Congress would need to supply new money if the wall is to be anywhere near completed, and Trump party has spent decades preaching fiscal prudence. Furthermore, much of the land needed to build the wall is privately owned, implying lengthy legal proceedings, political blow back, and substantial expropriation payments. Homeland Security Secretary John Kelly even told his confirmation hearing that the border wall might not be built anytime soon. Former officials said Trump could slow the process down by moving resources away from processing visa requests, or cut migrant quotas and programs. The orders would restrict immigration and access to the United States for refugees and visa holders from Iraq, Iran, Libya, Somalia, Sudan, Syria and Yemen.