Donald Trump tried to shield himself from rising legal heat on Thursday with tweets insisting that he never ordered his former lawyer Michael Cohen to break the law.The US president enters his third year in office facing an increasingly perilous situation as federal prosecutors and the special investigation into alleged collusion with Russia close in on him and his inner circle.But he was as combative as ever on Twitter when he sought to distance himself from his longtime former attorney, saying: "I never directed Michael Cohen to break the law".Cohen was sentenced on Wednesday in New York federal court to three years behind bars for crimes including illegal hush money payments to a porn actress and a Playboy model who allegedly had slept with the married Trump.Trump has denied having sexual relations with either of the women.But according to Cohen, the payments - which violated campaign finance laws - were designed to bury potential scandal at the height of the 2016 presidential campaign in which Trump surprised many by defeating his Democratic opponent Hillary Clinton.Cohen, who pleaded guilty to all the charges against him, told the court that he had felt it was his "duty to cover up ... (Trump's) dirty deeds."In his first public reaction since the sentencing, Trump said he was the victim of the attorney's malpractice."He was a lawyer and he is supposed to know the law," Trump tweeted. "It is called 'advice of counsel,' and a lawyer has great liability if a mistake is made. That is why they get paid."Later, he told Fox News in an interview that he was being singled out for a grilling over payments that would not cause a ripple elsewhere among politicians."Nobody except for me would be looked at like this, nobody," he said.I never directed Michael Cohen to break the law. He was a lawyer and he is supposed to know the law. It is called “advice of counsel,” and a lawyer has great liability if a mistake is made. That is why they get paid. Despite that many campaign finance lawyers have strongly......— Donald J. Trump (@realDonaldTrump) December 13, 2018 Trump's tweets on Thursday offered another layer of defense: that he had done "nothing wrong with respect to campaign finance laws, if they even apply, because this was not campaign finance".In other words, Trump argued that even if money was paid out, it had nothing to do with his campaign. That would mean that not only did he not commit a crime, but neither probably did Cohen - despite his guilty pleas."Cohen was guilty on many charges unrelated to me, but he plead to two campaign charges which were not criminal and of which he probably was not guilty even on a civil basis," Trump said.According to Trump, Cohen pleaded guilty to unfounded charges "to embarrass the president and get a much reduced prison sentence, which he did".....stated that I did nothing wrong with respect to campaign finance laws, if they even apply, because this was not campaign finance. Cohen was guilty on many charges unrelated to me, but he plead to two campaign charges which were not criminal and of which he probably was not...— Donald J. Trump (@realDonaldTrump) December 13, 2018 However, prosecutors paint a very different picture, tying the hush payments to the campaign and implicating the president in Cohen's crimes.The affairs allegedly happened years before, so the timing of the hush payments right before an election immediately raised questions.In the case of the Playboy model, Karen McDougal, her story was deliberately buried by the publishers of the National Enquirer tabloid newspaper, which is cooperating with prosecutors.American Media Inc publishers said in their cooperation deal that they were paid to "catch and kill," meaning they'd buy rights to embarrassing stories about Trump and then not publish.Trump, who is also trying to fend off a huge probe of his election campaign's contacts with numerous Russian officials, describes the mounting legal assault as a "witch hunt."Experts mostly agree that a sitting president cannot be indicted for alleged crimes, while Republican control of the Senate currently means that conviction in an impeachment trial would also be unlikely.In theory, Trump could be liable to prosecution once he leaves office.