WASHINGTON (AP) — Former CIA Director John Brennan said Thursday that President Donald Trump yanked his security clearance because his campaign colluded with the Russians to sway the 2016 election and is now desperate to end the special counsel's investigation.

In an opinion piece in The New York Times, Brennan cites press reports and Trump's own goading of Russia during the campaign to find Democrat Hillary Clinton's missing emails.

Trump himself drew a direct connection between the revocation of Brennan's clearance and the Russia probe, telling The Wall Street Journal the investigation is a "sham," and "these people led it!"

"So I think it's something that had to be done," Trump said.

Brennan wrote that Trump's claims of no collusion with Russia are "hogwash" and that the only question remaining is whether the collusion amounts to a "constituted criminally liable conspiracy."

"Trump clearly has become more desperate to protect himself and those close to him, which is why he made the politically motivated decision to revoke my security clearance in an attempt to scare into silence others who might dare to challenge him," he wrote.