Donald Trump warned ousted FBI Director James Comey on Friday not to talk to the media, a highly unusual move that prompted fresh charges the president is trying to silence the man who led an investigation into possible collusion between Trump's election campaign and Russia. On Twitter, Trump appeared to suggest that if Comey gave his version of contacts between them, the administration might produce tapes of conversations, although it was not clear if such tapes exist. The veiled threat added to the storm over Trump's abrupt firing of Comey on Tuesday. Critics have assailed Trump for dismissing the FBI chief just as the agency is investigating alleged Russian meddling in the 2016 US election, and possible Moscow ties to the Trump presidential campaign. The New York Times reported the president asked Comey in January to pledge loyalty to him and that Comey refused to do so. Such a request would undermine the standing of the FBI chief as an independent law enforcer and further fueled charges that Trump has overstepped the norms of his office. "James Comey better hope that there are no ‘tapes' of our conversations before he starts leaking to the press!" Trump said in a string of Twitter posts on Friday. Trump told Fox News he did not ask Comey to pledge loyalty and only wants him to be honest. Trump said he would not talk about the existence of any tapes. CNN said Comey is "not worried about any tapes" Trump may have, citing an unnamed source familiar with the matter. The Federal Bureau of Investigation probe and parallel congressional investigations have clouded Trump's presidency since he took office on Jan. 20, threatening to overwhelm his policy priorities. Democrats accuse the Republican president of trying to dent the FBI probe by firing Comey and have called for a special counsel to investigate the Russia issue. Trump also hit back on Friday at media reports questioning the credibility of White House accounts of why Comey was fired, which have changed over the course of the week, and threatened an end to regular White House press briefings. "As a very active President with lots of things happening, it is not possible for my surrogates to stand at podium with perfect accuracy!" Trump said. "Maybe the best thing to do would be to cancel all future ‘press briefings' and hand out written responses for the sake of accuracy???" Trump told Fox News he would decide in "the next couple of weeks" whether the briefings would continue. The White House initially said Trump fired Comey on the recommendation of the top Justice Department officials: Attorney General Jeff Sessions and Rosenstein. In the NBC interview on Thursday, Trump said he would have fired Comey regardless of any such recommendations. The White House has said Comey's firing was unrelated to the Russia probe. Seeking to bolster Trump's case that he has had no concealed dealings with Russia, his lawyers said in a letter released by the White House on Friday that a review of Trump's tax returns from the past 10 years showed no income from Russian sources outside of a few exceptions, and indicated he did not owe money to Russian lenders. — Reuters