Without mentioning who will pay for it, President Trump's new Secretary of Homeland Security told Fox News late Wednesday that he hopes the US-Mexico border wall can be built in two years.

As AFP reports, retired Marine general John Kelly told Fox...

"The wall will be built where it's needed first, and then it will be filled in. That's the way I look at it... I really hope to have it done within the next two years."

Trump has signed an executive order designed to meet his campaign pledge to build a wall along the 2,000 mile (3,200 km) southern US border, with the stated goal of keeping out undocumented migrants, drugs and criminals. Some 653 miles of border already features fencing that blocks people and/or vehicles.

Kelly said that protecting the southern border is "a layered approach" that includes physical barriers as well as technological sensors "and things like that".

Kelly, who will oversee the wall's planning and construction, said that the Trump administration officials "already have the authority" under existing law to start the project.

Trump has said that his cost estimates for building the wall range from $4 to $10 billion, but other estimates put the price at $11 billion for 400 more miles of fencing. The MIT Technology Review estimated that a 1,000 mile steel and concrete wall would cost $27 to $40 billion. Kelly was optimistic about what he called "the money aspect." "I think the funding will come relatively quickly," Kelly said, adding that construction could begin in just a few months.

While not commenting on the wall per se, former Mexican president Vicente Fox has been active on Twitter again this morning...