A military solution is "impossible" in parts of the Middle East, US CIA chief John Brennan said Tuesday, arguing that it was hard to picture effective central governments in some countries as they exist today.

Brennan, who spoke at an intelligence conference in Washington, was joined by other security officials and industry experts.

"When I look at Libya, Syria, Iraq and Yemen," Brennan said, "it's hard for me to envision a central government in those countries that's going to be able to exert control or authority over the territory that was carved out post World War II."

"A military solution is just impossible in any of these countries," he added.

"You need to be able to bring down the temperature, try to de-escalate the conflict, build up some trust between the parties that are there, that are seriously interested by a peace settlement" he said.

Bernard Bajolet, head of France's DGSE external intelligence agency, said the region was not likely to return to its old self following the current conflicts.

"The Middle East we have known is over, I doubt it will come back," he told the conference.

"We see that Syria is already divided on the ground, that the regime is controlling only a small part of the county, only one-third of the country which was established after WWII" he said.

"The north is controlled by the Kurds."

"We have the same thing in Iraq" Bajolet said, adding that "I doubt really that one can come back to the previous situation."

Nonetheless, he said he was "confident" that the region would one day stabilize again.