Trump says he'll bring down cost of Mexican wall

US President Donald Trump tweeted on Saturday that the media was wrong to say the cost of his promised wall along the United States' border with Mexico would be steeper than initially projected, promising that his negotiating skills will bring the price down sharply.

"I am reading that the great border WAll will cost more than the government originally thought, but I have not gotten involved in the design or negotiations yet. When I do, just like with the F-35 FighterJet or the Air Force One Program, price will come WAY DOWN!" EFE news quoted Trump as saying in a tweet.

The Twitter post about the wall was the President's first since January 26, when he reiterated that Mexico should pay for the barrier considering the US's large trade deficits with its southern neighbour stemming from the North American Free Trade Agreement (NAFTA), which he has repeatedly criticised as a one-sided deal.

Trump, who says the wall is necessary to thwart illegal immigration, also has accused Mexico of not doing enough to prevent undocumented migrants from crossing the border.

Mexican President Enrique Peña Nieto, who has vowed that his country will never pay for the wall, cancelled a scheduled visit to the US amid the flap, although he and Trump spoke by phone on January 27 and agreed not to publicly discuss funding for the border barrier.

The speaker of the US House of Representatives, Republican Paul Ryan, pledged in late January that the GOP-controlled Congress would approve funds for the wall and estimated it would cost between $13 billion and $15 billion.

But analysts at Bernstein, a research and brokerage firm, have put the wall's price tag at as high as $25 billion, or double the cost of a new highway linking the US's east and west coasts.

Since his surprise victory in the November 8 elections, the former real-estate mogul has secured commitments from lockheed Martin and Boeing to lower the cost of the F-35 Joint Strike Fighter programme and Air Force One programme, respectively.

He had criticised the costs of those programmes and threatened to cancel the orders.