US\u00a0President Donald Trump, who has repeatedly slammed a federal probe into possible collusion between Moscow and his presidential election campaign as a "witch hunt," said on Thursday he backed a "cooperative" approach to the investigation. "I have agreed with the historically cooperative, disciplined approach that we have engaged in with Robert Mueller," Trump said, referring to the special counsel leading the investigation. Mueller has been tasked with looking into allegations of Russian meddling in the 2016 presidential election. U.S. intelligence agencies have concluded that such interference took place, but Moscow denies it. Mueller is also investigating whether the Trump campaign colluded with Russia, which Trump has denied. Trump has repeatedly attacked the investigation, blaming it on Wednesday for Washington's frosty relationship with Moscow. The New York Times reported on Tuesday that he had tried to fire Mueller in December. Earlier on Thursday, Trump denied that report. "If I wanted to fire Robert Mueller in December, as reported by the Failing New York Times, I would have fired him," he said on Twitter. A bipartisan group of senators put forward legislation on Wednesday to protect Mueller and his investigation, which the Senate Judiciary Committee will consider next week.