Pentagon is without a chief as US faces many global threats

It's a difficult time for the Pentagon to be without a permanent US defence secretary.

The Trump administration is grappling with an escalating crisis with Iran, an unusual and controversial deployment of troops to the US-Mexico border, the nearly two-decade-old war in Afghanistan and stalled talks with North Korea over its nuclear weapons program.

Amid all that, and more, acting Defence Secretary Patrick Shanahan stepped down this week and the man tapped to replace him on an interim basis appears to face legal hurdles that could initially prevent him from serving more than about six more weeks.

It's an unusual level of uncertainty for one of the most important jobs in the administration.

"This is a very difficult time. With everything going on in Iran and all the provocations and counteractions, and to have no Secretary of Defence at this time is appalling," said Democratic Sen Chuck Schumer of New York.

"It shows the chaos in this administration. They have so many empty positions, revolving doors, in the most sensitive of security positions."
Trump has said he likes naming acting officials, telling reporters in January, "It gives me more flexibility."