Even as the scandal surrounding Saudi Arabia's role in the killing of journalist Jamal Khashoggi threatened one of the US's most important strategic alliances in the Middle East, Defense Secretary James Mattis remained conspicuously tight lipped about who bore responsibility for the killing, saying only that diplomatic crisis undermined stability in the region.

Well, one day after President Trump declared that the CIA could still very well determine that Saudi Crown Prince Mohammad bin Salman didn't know anything about the killing - despite Friday's Washington Post report claiming that the agency strongly believed that the order to kill Khashoggi came directly from the prince - Mattis defended his boss during a Pentagon press conference, saying that neither the CIA nor the Saudi government have "fully established" who was behind the killing. And even if the CIA could find definitive proof, it wouldn't change the fact that it's in the US's interest to work with the Saudis.

Because presidents don't always get to work with "unblemished" strategic partners, Mattis said. Furthermore, it's the president's duty to balance competing interests, and that Khashoggi's killers must be held accountable - but that the US must also work with the kingdom to end the humanitarian crisis in Yemen.

MATTIS to reporters in the Pentagon: "On the Khashoggi affair, presidents don't always get the freedom to work with unblemished partners in all things." — Katie Bo Williams (@KatieBoWill) November 21, 2018

Meanwhile, Saudi Foreign Minister Adel al-Jubeir played down reports about a rumored coup in Riyadh and said rumors about changing the line of succession were "ridiculous" and "way out of line," according to CNBC.

Given these remarks, and Trump's tweet from earlier Wednesday, we can expect oil prices to take another leg lower.