Border wall 'unlikely' to stretch 'from sea to shining sea,' says DHS head Apprehensions at the Southwest border dropped significantly last month.

 -- It is "unlikely" that the wall along the Southwest border of the United States will stretch "from sea to shining sea," Department of Homeland Security Secretary John F. Kelly said in a Senate hearing today.

Kelly is among several government officials who have now said that a "wall" across the entire border is not necessarily realistic. Instead the barrier will likely be some combination of wall, fencing, electronic surveillance and personnel, according to officials.

What the "wall" will look like -- including how tall and thick it will be -- is yet to be determined, Kelly said. It is "unlikely that we will build a wall or physical barrier from sea to shining sea," he continued, adding that he is "committed" to constructing a physical barrier wherever it is recommended.

Kelly said that President Donald Trump is aware of his plans to look "at every variation and theme" when drawing up plans for the wall.

"I have a lot of elbow room," he said.

On Wednesday, Customs and Border Protection released its apprehension numbers for the month of March, which continue to show a sharp decline.

Apprehensions -- used as an indicator of illegal border crossings -- were down 63 percent on the Southwest border: from 33,316 in March 2016 to 12,193 this past March, according to CBP.

The number of people apprehended on the Southwest border last month was down from 18,754 in February and 31,577 in January. In 2016, United States Border Patrol apprehended 408,870 people along the Southwest border, compared to 331,333 in 2015 and 479,371 in 2014, according to CBP.

During Wednesday's hearing, Kelly said that the U.S. has "seen an amazing drop in the number of migrants coming out of Central America that are taking that terribly dangerous route" from their home countries.

Kelly added that the reduction "won't last unless we do something again to secure the border."

Later in the hearing, Kelly explored other reasons why he thinks that fewer people are crossing the southwest border into the U.S., which include improving economic conditions in migrants' home countries and rising prices charged by coyotes helping to smuggle people across the border.