WASHINGTON (AP) — President Donald Trump has acknowledged it "certainly looks" as though missing Saudi journalist Jamal Khashoggi is dead, and he threatened "very severe" consequences if the Saudis are found to have murdered him. His warning came as the administration toughened its response to a disappearance that has sparked global outrage.

Before Trump spoke Thursday, the administration announced that Treasury Secretary Steven Mnuchin had pulled out of a major upcoming Saudi investment conference and a U.S. official said Secretary of State Mike Pompeo had warned the Saudi crown prince that his credibility as a future leader is at stake.

Pompeo said the Saudis should be given a few more days to finish and make public a credible investigation before the U.S. decides "how or if" to respond. Trump's comments, however, signaled an urgency in completing the probe into the disappearance of the journalist, last seen entering the Saudi Consulate in Istanbul on Oct. 2.

The messaging underscored the administration's concern about the effect the case could have on relations with a close and valuable strategic partner. Increasingly upset U.S. lawmakers are condemning the Saudis and questioning the seriousness with which Trump and his top aides are taking the matter, while Trump has emphasized the billions of dollars in weapons the Saudis purchase from the United States.

Turkish reports say Khashoggi, who had written columns critical of the Saudi government for The Washington Post over the past year while he lived in self-imposed exile in the U.S., was killed and dismembered inside the Saudi Consulate in Istanbul by members of an assassination squad with ties to Saudi Crown Prince Mohammed bin Salman. The Saudis have dismissed those reports as baseless but have yet to explain what happened to the writer.

Trump, who has insisted that more facts must be known before making assumptions, did not say on what he based his latest statement about the writer's likely demise.

Asked if Khashoggi was dead, he said, "It certainly looks that way. ... Very sad."

Asked what consequence Saudi leaders would face if they are found to be responsible, he replied: "It will have to be very severe. It's bad, bad stuff. But we'll see what happens."

Vice President Mike Pence said earlier in Colorado that "the world deserves answers" about what happened to Khashoggi, "and those who are responsible need to be held to account."

In Istanbul, a leaked surveillance photo showed a man who has been a member of the crown prince's entourage during trips abroad walking into the Saudi Consulate just before Khashoggi vanished there — timing that drew the kingdom's heir-apparent closer to the columnist's apparent demise.

Turkish officials say Maher Abdulaziz Mutreb flew into Istanbul on a private jet along with an "autopsy expert" Oct. 2 and left that night.

In Washington, Pompeo, who was just back from talks with Saudi and Turkish leaders, said of the investigations in Istanbul:

"I told President Trump this morning that we ought to give them a few more days to complete that so that we, too, have a complete understanding of the facts surrounding that, at which point we can make decisions about how, or if, the United States should respond to the incident surrounding Mr. Khashoggi."

Although Pompeo suggested the U.S. could wait longer for results, an official familiar with his meetings in Riyadh and Ankara said the secretary had been blunt about the need to wrap the probe up quickly.

The official, who was not authorized to publicly discuss details of the private meetings and spoke on condition of anonymity, said Pompeo told the crown prince that "time is short." The official added Pompeo had warned him that it would be "very difficult for you to be a credible king" without a credible investigation. The prince is next in line for the throne held by his aged father King Salman.

Shortly after Trump and Pompeo met at the White House, Mnuchin announced that after consulting the president and his top diplomat "I will not be participating in the Future Investment Initiative summit in Saudi Arabia."

The Saudis had hoped to use the forum, billed as "Davos in the Desert," to boost their global image. But a number of European finance ministers and many top business executives have pulled out as international pressure on Riyadh has intensified over Khashoggi.

Pompeo said that whatever response the administration might decide on would take into account the importance of the long-standing U.S.-Saudi partnership. He said, "They're an important strategic ally of the United States, and we need to be mindful of that."