Donald Trump says he’s hitting Iran with new and “substantial” sanctions after the U.S. accused Tehran of carrying out a drone strike on an important Saudi Arabian oil field. “I have just instructed the Secretary of the Treasury to substantially increase Sanctions on the country of Iran!” the president announced on Twitter on Wednesday morning. He didn’t specify what the new sanctions would entail. Iran has denied accusations from the Trump administration that it was behind Saturday’s attack on its huge Abqaiq oil-processing plant. Houthi rebels in Yemen said they were behind the strikes. However, the U.S. is adamant that Iran carried out the attacks and has issued satellite images and cited intelligence to back up its allegations. The incident cut global oil supplies by 5 percent and sent oil prices soaring.