CIA director John Brennan has warned Donald Trump that scrapping the nuclear deal with Iran would be "the height of folly" and "disastrous."

During a wide-ranging interview with the BBC that aired Wednesday, the outgoing U.S. spy chief also cautioned that Russia should not be trusted.

CIA Director John Brennan. JIM LO SCALZO / EPA

"First of all for one administration to tear up an agreement that a previous administration made would be unprecedented," Brennan said. “It would be the height of folly if the next administration were to tear up [the Iran] agreement."

Trump has promised to rip up the 2015 pact to curtail Iran’s nuclear program in exchange for an easing of international sanctions.

The Republican also expressed his admiration for Russian President Vladimir Putin during the campaign.

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Brennan also advised the incoming administration to be “wary of Russian promises.”

“Russia is a country that will pursue its national interests frequently to the detriment of the interests of the peoples of the countries wherein it operates,” he said. “Russian promises in my mind have not given us what it is they have pledged.”

During the campaign, Trump showed a lack of understanding of basic foreign policy concepts, and he was at times unable to distinguish between the Iranian Quds Force and the Kurdish people or to define the nuclear triad.