The president backed away from his threat to declare a national emergency over the wall, but his preoccupation with it persists

What exactly is Trump's border wall and why does he want $5.7bn for it?

Donald Trump may have backed away froma threat to declare a national emergency in order to bypass Congress and build a wall on the southern border, but his preoccupation with his 2016 campaign promise persists.

But what exactly is “the wall” and why is the president so intent on getting $5.7bn to fund it? Here are some answers to key questions:

What is the status of the wall?

The US-Mexico border is 1,954 miles (3,145km) long and crosses vast deserts and mountains in California, Arizona, New Mexico and Texas. About 654 miles of that have some sort of manmade barrier, such as fencing or a wall. Most of it was built after 2006.

So what does Trump want to do?

Details are thin on what would actually come from the $5.7bn. In recent weeks, Trump’s language has shifted from calling it a “wall” to a “barrier” and he has conceded it does not need to be concrete.

“The barrier or the wall can be of steel instead of concrete if that works better,” Trump said earlier this month. “I intend to call the head of United States Steel and a couple of other steel companies to have them come up with a plate or a design … we’ll use that as our barrier.”

Do Americans want a wall?

In January 2018, 60% of Americans said they opposed Trump’s proposal to substantially expand the wall, according to the Pew Research Center. Expanding the wall is more popular among older people, white people and the less educated, according to the survey.

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How many immigrants illegally cross the southern border?

There will never be an exact number because some people manage to cross illegally and undetected, then stay in the US, where they would not readily provide their immigration status to any sort of data collection.

That said, a good starting point is the number of people US Customs and Border Protection (CBP) apprehend at the southern border. In fiscal year 2017, that was 303,916 people, according to the Department of Homeland Security (DHS). Of that group, 13% claimed credible fear of returning to their home country, the first legal step in seeking asylum.

To put this in perspective, also in 2017, more than 606,926 people who entered the US legally by air or sea, not land, overstayed their visas and remained in the country at the end of the year, according to the DHS. And in 2000, 1.6 million illegal border crossers were apprehended.

The Trump administration has a habit of using “illegal” to describe completely legal actions, such as seeking asylum at the border. Influential, far-right immigration opponents, including people in senior positions in the Trump administration, oppose many aspects of the asylum process. They have worked to drastically restrict it, despite many of their efforts being blocked in the courts. Trump repeatedly refers to a crisis at the border and an “invasion” of migrants. He cites the wall as the primary solution, even though deep doubts abound about its efficacy.

Facebook Twitter Pinterest Children watch US immigration agents participate in a practice drill near the border wall in Tijuana, Baja California, Mexico, on 30 November 2018. Photograph: David Peinado/EPA

Do Democrats want open borders?

No. Trump and his supporters say Democrats support open borders (“Loopholes in our immigration laws, all supported by extremist open border Democrats,” Trump tweeted in June 2018), but Democrats have backed plenty of legislation that restricts immigration.

In February, the Senate voted on a bipartisan plan to spend $25bn over 10 years to expand the various physical barriers along the border and to protect the Dreamers, the estimated 3.6 million undocumented people who came to the US unlawfully as children. Trump rejected that bill.

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If the public doesn’t support the wall and the Democrats – who now control the House of Representatives – won’t acquiesce, why is Trump still demanding a wall?

The wall became a symbol for Trump’s presidency, a promise that he would limit immigration. The thing is, he has been very effective at making immigration more difficult for people trying to enter legally and illegally – yet the wall project still eludes him.

A hint to why he is so focused on getting this wall came in 2017, when the Washington Post published leaked transcripts from a private phone call between Trump and Mexico’s then president, Enrique Peña Nieto.

A week after taking office, Trump told Peña Nieto that he had to stop rejecting his claim that Mexico would pay for the wall, according to the transcripts. He suggested in the conversation that this was because the wall was more important as a symbol than as a national security project.

“I am just going to say that we are working it out,” Trump said. “Believe it or not, this is the least important thing that we are talking about, but politically this might be the most important”