President-elect Donald Trump's rhetoric will undermine the CIA through a "wave of resignations" and that will hamper its ability to work with foreign intelligence services, former Acting Director Michael Morell said.

"First, expect a wave of resignations," Morell, who served twice as acting director between 2010 and 2013, said in a Friday op-ed in The New York Times. "Attrition at the CIA, which has been remarkably low since Sept. 11, 2001, will skyrocket.

"The primary motivator for some of our smartest minds to go to work at the CIA is to make a difference to national security, to play a role in keeping the country safe," Morell said. "All of the sacrifices — from the long hours, polygraph tests, unfair media criticism, not to mention the real dangers to life and limb — are worth it, if you are making a difference."

The op-ed was published the same day the president-elect was briefed on a classified intelligence report saying that Russian President Vladimir Putin and his agencies meddled in the 2016 election in an attempt to sway the contest toward Trump.

Trump responded by slamming the report as a "political witch hunt," though he did say in a statement that the briefing was "constructive."

"While Mr. Trump’s statement on Friday … was a step in the right direction, his disparagement of American intelligence officers over the last few months is likely to cause significant damage to the CIA," Morell said.

"Trump's behavior will weaken the agency, an organization that has never been more relevant to our nation’s security," he concluded.

"The key national security issues of the day — terrorism; proliferation; cyberespionage, crime and war; and the challenges to the global order posed by Russia, Iran and China — all require first-rate intelligence for a commander-in-chief to understand them, settle on a policy and carry it out."