Senator Tim Kaine (D-VA) is calling on the Federal Bureau of Investigation to open an investigation into the murder of Jamal Khashoggi, the Washington Post journalist and Virginia resident who was killed inside the Saudi consulate in Istanbul after going missing in October 2018.

“This investigation is more important than ever to achieve true accountability and justice for this horrific crime,” Kaine said in a letter to FBI Director Chris Wray on Wednesday, which was obtained by The Daily Beast. The senator called Khashoggi’s killing a “state sponsored execution” by Saudi Arabia and requested written notification by August 1 from the FBI as to whether this investigation will take place.

The FBI declined to comment.

Kaine’s letter to Wray comes just weeks after the United Nations published a report on its six-month investigation into Khashoggi’s killing. In that report, the UN Special Rapporteur Agnes Callamard called Khashoggi’s dissapearance an “international crime” and said she found “credible evidence” that his murder was linked to the Saudi crown prince Mohammad Bin Salman. The CIA has also concluded with “high confidence” that the crown prince ordered the killing of Khashoggi.

Like Kaine, Callamard also recommended that the FBI open a probe “into the execution of Mr. Khashoggi, if one is not already open, and pursue criminal prosecutions within the United States, as appropriate.”

Over the past year, Congress has introduced several measures to investigate Khashoggi’s death and to hold those responsible accountable for it. This week lawmakers in the House voted for a bill to impose sanctions on officials involved in the killing. The bill, introduced by Rep. Tom Malinowski (D-NJ), requires the director of national intelligence to publicly name those involved and impose visa and travel sanctions on them.

Despite his own intel committee’s conclusions, President Donald Trump and his close aides have been reluctant to punish, let alone blame, the crown prince for his likely involvement in the Khashoggi killing. In an interview with NBC in June, Trump refused to commit to calling on the FBI to conduct an investigation into the matter, saying the situation has been “heavily investigated.”

The Trump administration has grown increasingly close with the crown prince and the Saudi Royal Court over the last two years. President Trump’s son-in-law Jared Kushner in particular is friendly with the crown prince and met with him several times in Saudi Arabia with little oversight from the State Department. The administration has read the country’s leaders in on U.S. regional policy proposals and decisions, including the development of Kushner’s Middle East peace plan.

And after the murder of Khashoggi, the Trump administration continued to work closely with Saudi Arabia. The administration moved ahead with doling out authorizations to U.S. companies who wanted to conduct nuclear-related work in the country, with two of those authorizations, known as Part 810s, being approved in the days following the Khashoggi murder. (Senator Kaine’s office was the first to reveal the timing of those authorizations.) And in May, the Trump team announced that it had approved a multi-billion dollar arms sales deal for Saudi Arabia.

In his letter to Wray, Kaine denounced the Trump administration for its inability to call out the crown prince and other leaders in Saudi Arabia for the murder of Khashoggi despite the overwhelming evidence against them, including evidence gathered by U.S. intelligence agencies.

And in hearings on Capitol Hill, lawmakers from both parties accused the Trump administration of bypassing Congress.

“For whatever reason, the administration, in what seems to me a not fully baked decision-making process, decided to circumvent the law, decided to circumvent the constitutional responsibility of Congress and act unilaterally,” Sen. Ted Cruz (R-TX) said in a recent hearing. “Don’t make the mistake of thinking that it is simply Democrats who are concerned about this.”