Pressure continues to build on Saudi Arabia to provide an explanation for the disappearance of dissident Jamal Khashoggi — and on the US to ensure it. Secretary of State Mike Pompeo arrived in Riyadh this morning and has already met with King Salman, exchanging warm greetings in public. “We are strong and old allies,” Salman told Pompeo, “so we face our challenges together — the past, the day of, tomorrow.”

Except for the consequences-from-killing-your-dissidents-in-your-diplomatic-facility part, presumably. That an ally can face on its own:

Secretary of State Mike Pompeo has arrived in Saudi Arabia after being dispatched by President Trump to meet with members of the royal court amid growing international tension over the disappearance of prominent Saudi journalist Jamal Khashoggi.

Pompeo met on Tuesday with King Salman bin Abdul-Aziz Al Saud in the Saudi capital and financial hub of Riyadh.

“Thank you for accepting my visit on behalf of President Trump,” Pompeo said on meeting the king. Details of the meeting were not immediately made public.

Pompeo will meet later Tuesday with Foreign Minister Adel al-Jubeir and Crown Prince Mohammed bin Salman, dining with the prince in the evening.

Yesterday, the New York Times, CNN, and later CBS reported that the Saudis were preparing an admission that an “interrogation” got out of hand, resulting in Khashoggi’s supposedly accidental death. So far, though, the admission has not yet been published. Perhaps Salman or his heir apparent, Mohammed bin Salman, wanted to wait for Pompeo to arrive before making this move. If so, they might expect Pompeo to publicly bless it as part of facing our challenges together, or something.

That explanation may no longer suffice. The UN human-rights office has called this morning for the Saudis to waive diplomatic immunity and to name everyone involved:

The U.N. human rights office is calling for the immediate and “absolute” lifting of diplomatic immunity enjoyed by any officials or premises in the investigation into the disappearance and suspected slaying of Saudi writer Jamal Khashoggi.

U.N. rights chief Michelle Bachelet said the “inviolability or immunity” of people or premises granted under the 1963 Vienna Convention on Consular Relations “should be waived immediately.”

She said Tuesday the “onus is on the Saudi authorities” to reveal what happened, and insisted “no further obstacles” should be placed in the way of a quick, thorough, impartial and transparent investigation.

Bachelet stopped short of calling for an international investigation.

Waiving diplomatic immunity and naming the personnel would likely create a major problem for the Saudis. As long as they can keep the names to themselves, no one can follow up on connections to higher-ranking officials. If any of the people involved in Khashoggi’s murder has a direct connection to bin Salman, it makes the “rogue killers” or “incompetent interrogators” cover story even more suspect than it already is. One would think that the Saudis would know better than to use anyone with those kinds of connections, but then again, it would have been assumed that they’d be smart enough not to kill a prominent dissident inside their own consulate.

However, the Saudis have already waived one aspect of diplomatic immunity: they have allowed Turkish investigators access to the consulate. Turkey’s president, Recep Tayyip Erdogan, told reporters that they’re now looking for “toxic materials” in the facility and in the consul’s residence, which will also be searched later today. It’s not clear what kind of “toxic materials” they expect to find, but it might have something to do with the theories about the removal of Khashoggi’s corpse after the murder.

Pompeo’s visit seems intended to do two things. It demonstrates that Donald Trump understands the seriousness of the moment, and it also allows the US to “face our challenges together” to bring the crisis to an end without damaging the anti-Iran front in the region. The upcoming arms sales package to Saudi Arabia still looms large in these calculations, but Sen. Marco Rubio tells CNN’s Alisyn Camerota that “human rights is worth blowing that up.” Khashoggi’s status as a permanent US resident means Saudi Arabia has to account to the US for his death, and that we can sell those arms to a number of other allies. “Any one of those factors is bad,” Rubio says after laying out the circumstances of the Khashoggi ambush. “Put them all together and it’s catastrophic” to credibility:

Update: The Saudi explanation plan is still on, NBC reports:

Saudi Arabia’s government is discussing a plan to admit that missing journalist Jamal Khashoggi was killed after entering the Saudi consulate in Istanbul, three people with knowledge of the situation tell NBC News.

According to two of the individuals, the Saudis are putting together an explanation that would absolve Crown Prince Mohammed bin Salman, the putative leader of Saudi Arabia, of responsibility by giving him plausible deniability to say he didn’t order the killing and didn’t know about it. …

One of those two individuals said he was told by those close to the Saudi leadership that the kingdom will claim that rogue operatives killed Khashoggi during an interrogation or a rendition attempt that went horribly awry. The third individual said the U.S. government still doesn’t know precisely what explanation the Saudis plan to give, but that the Saudis intend to admit “culpability.”

Will Pompeo allow them to float that explanation during his visit, or make them wait until after he leaves? That might give some insight into just how much Trump and Pompeo want to face this challenges “together” with the Saudis.