Mark Esper has become now the third person nominated to be the Army's top civilian leader by US President Trump.

The first two nominees dropped out — one over financial vetting issues and the other amid a backlash over controversial comments on LGBT issues.

Esper has been the top lobbyist for major defense contractor Raytheon since 2010. He also has experience working in the House and Senate, at the Pentagon and at the Heritage Foundation, a conservative think tank.

He graduated from the United States Military Academy at West Point, retired from the U.S. Army as a lieutenant colonel and is a veteran of the Gulf War, according to a Raytheon memo announcing his hiring.

Senate Armed Services Committee Chairman John McCain, who would handle Esper's confirmation process, has urged the Trump administration to put forward Pentagon nominees, but he could be wary of Esper's industry ties.

Trump's critics have raised questions about the number of lobbyists serving in his administration despite his pledge to "drain the swamp."