The Turkish fiancée of slain journalist Jamal Khashoggi asked U.S. lawmakers on Thursday to launch an investigation into his killing and bring those responsible to justice.

"I cannot understand [why] the world still has not done anything about this," Hatice Cengiz told a congressional panel through a translator. Speaking in her native Turkish, she said the very ideals of the United States are at stake in the way the country responds to Khashoggi's killing.

"It wasn't just Jamal that was killed, it was also ... the values of the United States," she said.

Khashoggi, a Washington Post columnist who wrote critically of Saudi Arabia's crown prince, was killed by agents of the kingdom in October after he entered a Saudi consulate to collect marriage documents. The killing, and U.S. President Donald Trump's muted response to it, sparked outrage in Congress among both parties.

Cengiz delivered emotionally raw testimony to the small group of lawmakers, describing the plans she and Khashoggi had to move to Washington together after their marriage.

Jamal Khashoggi, a Washington Post contributor, was killed in October 2018 after a visit to the Saudi consulate in Istanbul to obtain paperwork he needed to marry his Turkish fiancée. (Yasin Akgul/AFP/Getty Images)

"If someone told me that I would come here without Jamal to ask about justice for him, I would not have believed it," she said. "Jamal told me that Washington was a beautiful city and we would lead a beautiful life."

Partly in response to a growing appetite to reassess the U.S.-Saudi alliance, Congress passed legislation this year to end U.S. involvement in the Saudi-led war in Yemen. Trump vetoed the bill.

A trial is underway in Saudi Arabia for 11 people charged in the killing, but it's taking place largely behind closed doors. Human rights advocates have raised concerns and called for greater transparency from the Saudi government.