UPDATED 8.29AM US President Donald Trump today signed his latest executive order to build the wall along the border with Mexico, which the White House still says Mexico will pay for "one way or another".

"Building this barrier is more than just a campaign promise. It's a common sense first step to really securing our porous border," said White House spokesman Sean Spicer on Wednesday.

"This will stem the flow of drugs, crime, illegal immigration into the United States."

He said the orders will strip federal money from so-called sanctuary cities and end a "catch and release" policy of previous administrations.

LISTEN ABOVE: Chris Rudolph, Associate Professor of International Relations at American University, speaks with Rachel Smalley

President Trump expects the construction of the US-Mexico border wall to start "in months" and that planning is already underway, according to excerpts of an interview with ABC News.

Trump told the television network that while US taxpayers would have to initially fund the wall, Mexico would ultimately pay for it, adding that negotiations for the reimbursement would start "relatively soon".

In the coming days, Trump is expected to limit the number of refugees admitted to the United States to 50,000 a year, down from 100,000, and to impose a temporary ban on most refugees.

Trump, who took office last Friday, will begin signing the orders at the Department of Homeland Security on Wednesday.

On Twitter on Tuesday night, Trump reiterated his promise to build the border wall, which was a cornerstone of his presidential campaign and which he has promised to make Mexico pay for.

Big day planned on NATIONAL SECURITY tomorrow. Among many other things, we will build the wall!

— Donald J. Trump (@realDonaldTrump) January 25, 2017

The border enforcement order includes plans to hire 5000 more US Customs and Border Protection agents used to apprehend migrants at the border and to triple the number of US Immigration and Customs Enforcement Agents used to arrest and deport migrants living in the United States illegally.

The Customs and Border Protection agency has already struggled to meet its hiring mandate, with a little more than 19,000 agents on the payroll, out of a congressionally mandated 21,000.

Immigration enforcement away from the border is also expected to be strengthened by seeking an end to "sanctuary cities" where local law enforcement officials refuse to cooperate with federal immigration authorities.

Trump will call for an end to this practice and may instruct the federal government to stop providing certain funds to cities that refuse to comply.

Later in the week, Trump is expected to suspend the issuing of visas to people from countries where it is deemed that adequate screening cannot occur.

Immigration experts expect those countries to include Syria, Sudan, Somalia, Iraq, Iran, Libya and Yemen.

A review will be conducted by the Trump administration to determine what screening must occur before travel for citizens from such countries can resume.