The CIA has concluded that Saudi Crown Prince Mohammed bin Salman ordered the assassination of journalist Jamal Khashoggi in Istanbul last month, contradicting the Saudi government’s claims that he was not involved in the killing, according to people familiar with the matter.

The CIA’s assessment, in which officials have said they have high confidence, is the most definitive to date linking Mohammed to the operation and complicates the Trump administration’s efforts to preserve its relationship with a close ally. A team of 15 Saudi agents flew to Istanbul on government aircraft in October and killed Khashoggi inside the Saudi consulate, where he had come to pick up documents that he needed for his planned marriage to a Turkish woman.

In reaching its conclusions, the CIA examined multiple sources of intelligence, including a phone call that the prince’s brother Khalid bin Salman, the Saudi ambassador to the United States, had with Khashoggi, according to the people familiar with the matter who spoke on the condition of anonymity to discuss the intelligence. Khalid told Khashoggi, a contributing columnist to The Washington Post, that he should go to the Saudi consulate in Istanbul to retrieve the documents and gave him assurances that it would be safe to do so.