Donald Trump's wall 'different than a fence'

US Secretary of Homeland Security Kirstjen Nielsen
US Secretary of Homeland Security Kirstjen Nielsen introduces the wall/fence. Photo credit: Reuters

The builders of the first section of Donald Trump's controversial border wall are defending accusations it looks more like a fence.

The 4km-long, 9m-high section took eight months to build, and it has a plaque with Donald Trump's name on it beneath the Great Seal of the United States.

But it's not a solid wall - instead a series of steel posts with a gap a cat could easily slink through.

Mr Trump has previously denied the wall would be a fence.

"It's not a fence. It's a wall," he said in January 2017.

US Secretary of Homeland Security Kirstjen Nielsen, who unveiled whatever it is to media on Monday (NZ time), also said it was not a fence.

"It's different than a fence in that it also has technology. It's a full wall system," she said. "It's a wall, this is what the President has asked us to do. It's part of a system."

She went on to say she wouldn't attempt to climb it.

Only US$38 million has been set aside this year for wall construction. The total cost of the wall, which will need to be 786 times longer if it's to cover the entire border with Mexico, is estimated to cost potentially more than US$30 billion.