It was the controversial campaign promise that Donald Trump built his 2016 electoral success on: to build what he called a “big beautiful wall” on the US border with Mexico.

But, two and half years after he took office, supporters – who were so enamoured by the idea, they regularly chanted in favour of the structure – may be forgiven for wondering where exactly it is.

Now, it has emerged that not a single new stretch of border wall has been built since Mr Trump took office in January 2017.

A statement released by the US Customs and Border Protection (CBP) agency confirmed the 51 miles of fencing completed since Mr Trump took power has simply replaced barriers that already existed.

No original wall or fencing has been created in areas that previously did not have any, it said.

Trump shuts down US government over Mexico border wall – in pictures Show all 15 1 /15 Trump shuts down US government over Mexico border wall – in pictures Trump shuts down US government over Mexico border wall – in pictures Federal workers and contractors rally against the partial federal government shutdown Getty Images Trump shuts down US government over Mexico border wall – in pictures The US Capitol on the first morning of a partial government shutdown in Washington EPA Trump shuts down US government over Mexico border wall – in pictures Federal workers and contractors rally against the partial federal government shutdown Getty Trump shuts down US government over Mexico border wall – in pictures President Trump speaks with children who called the North American Aerospace Defense Command Santa tracker in the State Dining Room of the White House. He earlier in the day, tweeted that he was 'all alone in the White House' waiting for Democrats to make a deal on border security EPA Trump shuts down US government over Mexico border wall – in pictures Furloughed federal workers pick up free food at a pop-up store of Kraft Heinz Getty Images Trump shuts down US government over Mexico border wall – in pictures Hundreds of federal workers and contractors rally against the partial federal government shutdown Getty Trump shuts down US government over Mexico border wall – in pictures A pedestrian walk past the U.S. Capitol ahead of a possible partial government shut down in Washington, U.S., December 20, 2018. REUTERS/Joshua Roberts JOSHUA ROBERTS Reuters Trump shuts down US government over Mexico border wall – in pictures From left, House Majority Leader Steny Hoyer, Senate Minority Leader Chuck Schumer, Sen. Dick Durbin and Speaker of the House Nancy Pelosi walk to speak to reporters after meeting with President Donald Trump about border security in the Situation Room of the White House. Trump declared he could keep parts of the government shut down for "months or even years" as he and Democratic leaders failed in a second closed-door meeting to resolve his demand for billions of dollars for a border wall with Mexico Evan Vucci AP Trump shuts down US government over Mexico border wall – in pictures Federal workers and contractors rally against the partial federal government shutdown Getty Images Trump shuts down US government over Mexico border wall – in pictures A sign alerts visitors to the closure of the National Archives on the fifth day of a partial government shutdown EPA Trump shuts down US government over Mexico border wall – in pictures Hundreds of federal workers and contractors rally against the partial federal government shutdown Getty Images Trump shuts down US government over Mexico border wall – in pictures Visitors read signs announcing the closure of the White House Visitor Center EPA Trump shuts down US government over Mexico border wall – in pictures President Donald Trump speaks during a round-table discussion on border security and safe communities with State, local, and community leaders in the Cabinet Room of the White House Getty Images Trump shuts down US government over Mexico border wall – in pictures A sign alerts visitors to the closure of the White House Visitor Center on the first day of a partial government shutdown EPA Trump shuts down US government over Mexico border wall – in pictures Furloughed federal workers show their IDs for entering a pop-up store of Kraft Heinz Getty Images

That is despite the fact that a total of 205 miles of both new and replacement wall and fencing has already been budgeted for since Mr Trump took office – including via the Treasury Forfeiture Fund which the president redirected through controversial executive action in February.

Speaking anonymously to the Washington Examiner, a senior official in the Trump administration said engineers could move faster on so-called replacement projects than entirely new stretches of fence because the approval process for environmental and zoning permits was less extensive.

Another official blamed Democrats for obstructing progress. He told the newspaper: “The wall projects are moving along as quickly as practicably possible given the unprecedented obstruction from Democrat lawmakers to protect and prolong open borders.”

Yet it seems the lack of progress will not deter Mr Trump from making the wall a central part of his 2020 election campaign.

When crowds took up their now familiar refrain of “build that wall" at a recent rally in El Paso, Texas, Mr Trump responded by telling them: “Now, you really mean 'finish that wall,' because we've built a lot of it.”

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The CBP recently said it will be continuing to build the approximately 205 miles of wall that have been funded so far this year, using Treasury Forfeiture Fund money that Mr Trump seized in February after the partial government shutdown.