(Reuters) -Lawyers for Saudi Arabian Crown Prince Mohammed bin Salman, facing a U.S. lawsuit over the 2018 killing of Saudi journalist Jamal Khashoggi, told a court on Monday the crown prince's appointment as prime minister last week ensured him immunity from prosecution.
Khashoggi was killed and dismembered by Saudi agents in the Saudi consulate in Istanbul in an operation which U.S. intelligence believed was ordered by Prince Mohammed, who has been the kingdom's de facto ruler for several years.
The prince denied ordering Khashoggi's killing, but acknowledged later it took place "under my watch."
Last week his elderly father King Salman named him prime minister in a royal decree which a Saudi official said was in line with responsibilities the crown prince was already exercising.
"The Royal Order leaves no doubt that the Crown Prince is entitled to status-based immunity," lawyers for the prince said in a petition requesting a federal district court in Washington dismiss the case, citing other cases where the United States has recognised immunity for a foreign head of state.
U.S. President Joe Biden, who fist-bumped the crown prince on a visit to Saudi Arabia in July to discuss energy and security issues, had told Prince Mohammed that he considered him responsible for Khashoggi's killing.
He said Prince Mohammed denied involvement and asserted those involved had been held to account.
Khashoggi, who had criticized the crown prince's policies in Washington Post columns, had traveled to the Saudi consulate in Istanbul to obtain papers he needed to marry Hatice Cengiz, a Turkish citizen.
The lawsuit was filed jointly by Cengiz and a human rights group founded by Khashoggi, and sought unspecified damages against the crown prince, known in the West as MbS. It also named more than 20 other Saudis as co-defendants.
It charged that MbS, his co-defendants and others carried out a plot to "permanently silence Mr. Khashoggi" after discovering he planned to use the group as "a platform to espouse democratic reform and promote human rights."
The court had asked the U.S. Department of Justice to express a view on whether Prince Mohammed had immunity, setting an Oct. 3 deadline for a response.
After the prince's appointment as prime minister last week, the department said on Friday it was seeking a 45-day extension to prepare its response to the court "in light of these changed circumstances."
On Monday, U.S. District Judge John D. Bates granted the request for an extension but said absent compelling evidence, this would be the only extension he would allow.
The United States should file any statement of interest no later than Nov. 17, Bates said in a court document.