WASHINGTON — President Trump said Wednesday the U.S. is "demanding" answers from Saudi Arabia about the disappearance of a well-known Saudi writer. Mr. Trump said he plans to invite to the White House the fiancée of Jamal Khashoggi, a writer for The Washington Post who has not been seen since he entered the Saudi consulate on Oct. 2 to get paperwork for his marriage.

Turkish authorities say Khashoggi — a government critic who has been living in self-imposed exile in the U.S. for the past year after fleeing a crackdown on intellectuals and activists in the country — was slain inside the consulate. A newspaper close to the Turkish president published photos Wednesday of what it said was a 15-member "assassination squad" allegedly sent to target Khashoggi.

Saudi Arabia, however, denies involvement in his disappearance. The Saudi ambassador to Washington, Prince Khalid bin Salman bin Abdulaziz, described the allegations as "malicious leaks and grim rumors" and said the kingdom is "gravely concerned" about Khashoggi. Saudi officials maintain he left the consulate shortly after entering, although it has failed to provide evidence.

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Mr. Trump told reporters in the Oval Office that the White House is in contact with Khashoggi's fiancée, Hatice Cengiz, who was waiting outside the consulate when Khashoggi went inside earlier this month. She has since appealed to the president and first lady Melania Trump for help.

Mr. Trump said nobody knows exactly what happened and expressed hope that Khashoggi is not dead. He also said he had spoken with the Saudis about what he called a "bad situation," but he did not disclose details of his conversations.

Mr. Trump's comments Wednesday were the toughest yet from his administration on the case.

President Trump on Oct. 10, 2018, in the Oval Office. Getty Images

Analysts said there were reasons for skepticism about the Turkish account of what happened. Ties between Ankara and Riyadh are at a low point over Turkey's support for Qatar in that country's yearlong dispute with Saudi Arabia and other Gulf nations. Saudi Arabia, a Sunni Muslim power, is also annoyed by Ankara's rapprochement with the kingdom's Shiite archrival, Iran.

However, Saudi authorities' failure to provide video footage of Khashoggi's movements at the consulate to rebut the Turkish allegations have only deepened suspicions.

Members of Congress have grown increasingly insistent that the administration find out what occurred. Some lawmakers warn that relations between the Saudi Arabia and the U.S. could be jeopardized if it turns out the kingdom was involved in Khashoggi's disappearance.

While angry members of Congress likely won't cause the administration to turn away from Saudi Arabian Crown Prince Mohammed bin Salman and end decades of close security ties with Saudi Arabia, they could throw a wrench into arms sales that require their approval and demand the U.S. scale back support for the Saudi military campaign against Iran-backed rebels in Yemen.

Republican Sen. Bob Corker of Tennessee, chairman of the Senate Foreign Relations Committee, said "there will definitely be consequences" if it turns out the Saudis were involved in Khashoggi disappearance. Republican Sen. Lindsey Graham of South Carolina said it would be "devastating" to the U.S.-Saudi relationship.

Sen. Chris Murphy, D-Conn, said if Saudi Arabia had lured a U.S. resident into a consulate and killed him, "it's time for the United States to rethink our military, political and economic relationship with Saudi Arabia." But he said it was unclear whether the Trump administration was willing to "go beyond words."

Sen. Rand Paul, R-Ky., a longtime critic of the Saudi government, said he'll try to force a vote in the Senate this week blocking U.S. arms sales to Saudi Arabia. He told local radio in his home state Tuesday that he wants to end the arms shipments if there's "any indication" the Saudis are "implicated in killing this journalist that was critical of them."

White House press secretary Sarah Huckabee Sanders said White House national security adviser John Bolton and White House senior adviser Jared Kushner spoke on Tuesday to Crown Prince Mohammed about Khashoggi. Secretary of State Mike Pompeo then had a follow-up call with the crown prince to reiterate the U.S. request for information.

In an interview with radio host Hugh Hewitt that aired Wednesday, Vice President Mike Pence said the missing Saudi writer's fate was "a great concern for the United States of America." Asked if the U.S. would send an FBI team to help in the investigation — if the Saudis requested such assistance — Pence said, "the United States of America stands ready to assist in any way.

"But as I said yesterday, the free world deserves answers," Pence said. "And the reports that a Saudi Arabian journalist may have been tragically murdered in Turkey should be deeply concerning to everyone who cherishes a freedom of the press and human rights across the globe."

The Trump administration is heavily invested in the Saudi relationship. That's unlikely to change, said Robin Wright, a scholar at the Wilson Center think tank and close friend of the missing writer. The administration's Middle East agenda heavily depends on the Saudis, including efforts to counter Iranian influence in the region, fight extremism and build support for an expected plan for peace between Israel and the Palestinians.

Indication of those stakes came within four months of Mr. Trump taking office, when Saudi Arabia became his first destination on a presidential trip and he announced $110 billion in proposed arms sales.

Prince Mohammed has introduced some economic and social reforms, allowing women to drive and opening movie theaters in the deeply conservative Muslim nation. The flip side, however, is that he's also squelched dissent and imprisoned activists. He has championed the three-year military campaign against Iranian-backed Houthi rebels in Yemen that has pushed that nation toward famine and caused many civilian deaths.

Still, the Trump administration last month stood behind its support for that campaign with weapons, logistics and intelligence, certifying that the Saudis were taken adequate steps to prevent civilian despite mounting evidence to the contrary.

Karen Elliott House, a veteran writer on Saudi affairs and chair of the board of trustees at RAND Corp., said U.S. support for the Yemen war is likely to be the focus of congressional criticism but won't endanger a relationship that has endured for decades, underpinned by shared strategic interests. Even under the Obama administration, which had difficult relations with Riyadh compared with Mr. Trump, there were some $65 billion in completed arms sales.

"The U.S.-Saudi relationship is certainly not about shared moral values," House said. "It's about shared security interests."