What's happening with the wall Trump promised on the Mexican border?
"Drugs are pouring into our country at a record pace," he said. "A lot of people coming in that we can’t have.”
Throughout Mr Trump’s presidential election campaign, he called for a large, impenetrable wall to be constructed between the US and Mexico.
One year since Mr Trump took office, here’s a round-up of what has happened to his project so far.
What did Trump promise for the Trump-Mexico border wall?
The president’s pledge to build a border wall dates back to the announcement of his candidacy in June 2015, in an incendiary speech he delivered at Trump Tower in New York.
“When Mexico sends its people, they're not sending their best,” he said. “They're sending people that have lots of problems… They're bringing drugs. They're bringing crime. They're rapists.”
He promised to build a wall spanning the 2,000-mile border to keep migrants out.
“I would build a great wall, and nobody builds walls better than me, believe me, and I’ll build them very inexpensively, I will build a great, great wall on our southern border. And I will have Mexico pay for that wall.”
How much will the Trump-Mexico border wall cost?
This week, the Trump administration said it wants $18bn (£13bn) over the next decade, for the initial phase of the border wall. This is considerably more than Mr Trump’s initial cost estimate of around $10bn.
The $18bn, first reported by the Wall Street Journal, would go towards 316 miles of new fencing and reinforcing another 400 miles of existing barriers, according to cost estimates by US Customs and Border Protection (CBP).
If this work goes ahead, more than half of the border with Mexico will have a wall - or similar structure - by 2027.
There are considerable extra costs, however. The CBP also requested $8bn for additional personnel and training, plus $5bn for new border technology and another $1bn to construct access roads. This puts the final spend at $33bn over the next ten years.
Who will pay for the Trump-Mexico border wall?
When President Trump first mentioned the wall, he claimed Mexico would foot the bill. The Mexican government has repeatedly said it will not pay for the border wall.
Last week, however, Mr Trump reiterated his plan during a news conference at Camp David, the presidential country retreat in Maryland.
“I believe Mexico will pay for the wall,” Mr Trump said. “I have a very good relationship with Mexico. But yes, in some form, Mexico will pay for the wall.”
A report from the US Department of Homeland Security in February 2017 revealed the border wall could cost American taxpayers a total of $21.6bn (£17.3bn).
Will the Trump-Mexico border wall actually be built?
In September 2017, construction on eight wall prototypes - measuring between 18-30 feet high - was started in San Diego, the CBP announced.
Ronald Vitiello, acting deputy commissioner of the CBP, said: “We are committed to securing our border and that includes constructing border walls. Our multi-pronged strategy to ensure the safety and security of the American people includes barriers, infrastructure, technology and people.
“Moving forward with the prototypes enables us to continue to incorporate all the tools necessary to secure our border."
These eight prototypes are still in San Diego, however, and whether the the wall will ever actually be fully constructed is far from certain.
In February 2017, an internal Department of Homeland Security report obtained by Reuters estimated the wall will take three-and-a-half years to complete.
This is unlikely, critics say because the funding still has to be approved by Congress.