A 30-foot fence high spanning two miles has been constructed at the Mexico-US border.

Sporting a plaque that boasted President Donald Trump's name, it marks the first phase of a wall to block migrants from entering the US.

Homeland Security Secretary Kirstjen Nielsen inaugurated the Calexico site in Imperial City, California Friday.

She warned 'everything is on the table' as the administration considered new measures to send a message to a dwindling and slow-moving migrant caravan from Honduras. It is currently 990 miles away from McAllen, Texas.

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A 30-foot fence spanning two miles was erected in Imperial City, California Friday

Border Patrol agents stood next to a new stretch of border wall in Calexico, California

Homeland Security Secretary Kirstjen Nielsen spoke at the Mexico-US border as a migrant caravan from Honduras was 990 miles away from McAllen, Texas

'Let me be clear: Walls work,' Nielsen said after workers fixed a plaque to the barrier which featured names several high-ranking officials including herself and Trump.

'We are looking at every possible way within the legal construct that we have to make sure that those who don't have the legal right to come to this country do not come in.'

The structure is separate from a concrete wall prototype built near San Diego as part of Trump's signature White House campaign promise in 2016.

The mission is expected to run October 30 to December 15 in California, Arizona and Texas

Further confirming the travelers will not be welcome, the Pentagon approved a request for additional troops at the southern border. It means there could be 800 to 1,000 joining in total.

The troops are not the same National Guard members that responded to a spike in illegal border crossings this year. Those focused on surveillance and were under the control of the governors in the states they're positioned.

There are currently approximately 2,000 National Guard troops on the border.

The structure is separate from a concrete wall prototype built near San Diego as part of Trump's signature White House campaign promise in 2016

Nielsen spoke after workers fixed a plaque to the barrier which featured names several high-ranking officials including Trump

Javier Caro, left, and Michael Nolta attach a plaque to the newly fortified border wall structure

An anonymous Defense Department official said the mission is expected to run from October 30 to December 15 in California, Arizona and Texas and added the troops will not be involved in detaining migrants.

The Pentagon said as well as barricades and fencing, helicopters and airplanes will move Border Patrol personnel, and medical teams to triage and treat patients and prepare them for commercial transport.

It also will provide personal protective gear and temporary housing for personnel.

Meanwhile anonymous White House sources told the Associated Press border security may start using measures akin to the travel ban that made it very difficult for passengers flying from many Islamic countries, or blocked those who held passports from them, entering the US.

The two insiders said it was still in the early planning stages and had yet to be decided.

Names on the plaque included: Gloria I. Chavez, Chief Al Centro Sector, Carla L. Provost, Chief US Border Patrol, Kevin K. McAleenan, Commissioner US Customs and Border Protection

The structure is separate from a concrete wall prototype built near San Diego as part of Trump's signature White House campaign promise in 2016

Nielsen also called for more funding for the wall Friday as the US was 11 days away from the mid-term elections.

'Border security is national security. We need funding to continue building @POTUS' wall. We need personnel to secure the border. And we need laws that work for the American people,' she tweeted. 'I refuse to believe that this is too complex for Congress to solve, they must address this crisis.'

In a separate tweet she thanked the US Customs and Border Patrol in El Centro.

'Very proud today to acknowledge the completion of the first section of POTUS' and all our partners that are helping us to deploy new border wall systems,' she posted.

'Thank you @CBPElCentro and all our partners that are helping us to deploy new border wall systems.'

US Department of Homeland Security Secretary Kirstjen Nielsen thanked the US Customs and Border Patrol in El Centro

Nielsen called for more funding into the wall Friday as the US was 11 days away from the mid-term elections

Meanwhile Trump had a warning for migrants as he spoke at a meeting of young black conservative leaders in the White House the same day.

He said: 'I called up the military. We're not letting them in, they ought to go back now because we're not.'

However Andrea Guerrero, executive director of Alliance San Diego, said it would be 'a very drastic action that would have disastrous practical implications for our asylum obligations, for our moral and legal obligations.'

'We know that civil rights attorneys are preparing to litigate right now,' she told AP. 'They're preparing to litigate right away. I don't know if (Trump) cares if he wins the litigation. He wants to score political points ... it's all part of the same political ploy to stoke fear for political reasons and build more walls.'