President Trump’s legal team is now demanding that special counsel Robert Mueller provide proof that the president committed a crime before he’ll agree to sit down for an interview, The New York Times reports. Rudy Giuliani, Trump’s lead lawyer for the Russia investigation, reportedly said Mueller would also have to prove that the president’s testimony is crucial to wrapping up the investigation. Though Trump had previously vowed to cooperate with the probe, the ultimatum appears to be just the latest effort by his legal team to undermine it. Giuliani conceded that Mueller will probably not agree to the latest demands. “If they can come to us and show us the basis and that it’s legitimate and that they have uncovered something, we can go from there and assess their objectivity,” Giuliani told the Times. Behind the scenes, Trump’s legal team has also reportedly blocked Mueller’s team from interviewing White House chief of staff John Kelly, who is said to be willing to testify.