The director of the CIA, John Brennan, has launched a review into overhauling the American spy agency, in a bid to improve its effectiveness.

While no "singular threat" was said to have triggered the review, the US war against the Islamic State in the Middle East has reportedly frustrated the director, compelling him to improve intelligence gathering in the region.

Brennan said: "I have become increasingly convinced that the time has come to take a fresh look at how we are organized as an agency and at whether our current structure, and ways of doing business, need adjustment to ensure our future success."

The current proposals would assign different regions to different units, according to the Washington Post, in a structure reminiscent of the agency’s Counterterrorism Center and other similar groups in the CIA.

Investigators began work on the review in September, and have still not decided which options will be on the table, or whether those outlined above would go ahead.

"We’re in a time when there are an incredible number of diverse threats, ranging from cyber to threats in the Middle East, to Ukraine, and others," CIA spokesman Dean Boyd told the Agence France-Press.

"We need to periodically evaluate ourselves so we are best positioned to meet these and future challenges."