US President Barack Obama will on Friday nominate Jeh Johnson, formerly the Pentagon's top lawyer, to lead the Department of Homeland Security, an official said.
Johnson, who will succeed Janet Napolitano who left earlier this year, was in his previous job responsible for a prior legal review of every military operation ordered by the president or the secretary of defense.
"The President is selecting Johnson because he is one the most highly qualified and respected national security leaders, having served as the senior lawyer for the largest government agency in the world," a US official said.
Johnson was also part of a review team behind the repeal of the "Don't Ask, Don't Tell" prohibition on gays serving openly in the military, earlier in the Obama administration.
Johnson was also involved in legal decisions surrounding the US drone program that has targeted terror suspects, and other key military operations.
The Homeland Security Department was set up after the September 11 attacks in 2001, and is responsible for counter-terror operations and protection on US soil.
It also oversees border enforcement, agencies including the Secret Service and works to combat natural disasters such as hurricanes.
Johnson served as the Defense Department's general counsel during Obama's first term.
His nomination must be confirmed by the Senate.