President Trump has told advisers he is eager to strip more security clearances as part of an escalating attack against foes who have criticized him or played a role in the probe of alleged Russian interference in the 2016 election, according to two White House officials.

Over the past 19 months, Trump has fired or threatened to take actions against nearly a dozen current and former officials associated with the investigation he has labeled a “rigged witch hunt,” including former FBI director James B. Comey and other top FBI officials Sally Yates and Andrew McCabe. All three were dismissed.

Trump intensified his attacks this week by stripping former CIA director John Brennan of his security clearance and announcing that others were under review. Brennan and former Director of National Intelligence James R. Clapper Jr., who is on Trump’s review list, were among the Obama administration officials who briefed Trump before his inauguration on evidence of Russia’s interference in the election.