The fiancé of Jamal Khashoggi has launched a scathing attack on the US government over its handling of her partner’s killing by Saudi Arabian officials, branding the Trump administration “devoid of moral foundation”.

Hatice Cengiz, in a column for the Washington Post, called on the international community to bring her partner’s killers to justice and to find his missing body, which Turkish authorities say was dissolved in acid.

Ms Cengiz’s op-ed was published exactly a month after Mr Khashoggi failed to reappear from the Saudi consulate in Istanbul on 2 October. Turkey alleges he was murdered by a hit squad authorised by the “highest levels” of the Saudi government.

Istanbul's chief prosecutor announced on Wednesday that Mr Khashoggi was strangled immediately after he entered, before his body was dismembered and removed from the consulate.

The Saudi government initially insisted Khashoggi had left the consulate, later saying he died in an unplanned "rogue operation". Last week, the kingdom's public prosecutor, Saud Al Mojeb, said the attack was premeditated.

“It is now up to the international community to bring the perpetrators to justice,” Ms Cengiz wrote. “Of all nations, the United States should be leading the way. The country was founded on the ideals of liberty and justice for all, the First Amendment enshrining the ideals personified by Jamal.

Justice for Jamal Khashoggi protest outside the Embassy of Saudi Arabia

“But the Trump administration has taken a position that is devoid of moral foundation. Some have approached this through the cynical prism of self-interest — statements framed by fear and cowardice; by the fear of upsetting deals or economic ties.

“Some in Washington are hoping this matter will be forgotten with simple delaying tactics. But we will continue to push the Trump administration to help find justice for Jamal. There will be no cover-up.”

Donald Trump has condemned the killing, but has also defended US arms sales to Saudi Arabia, which is the biggest foreign customer for American weaponry.

Jamal Khashoggi death: key figures Show all 7 1 /7 Jamal Khashoggi death: key figures Jamal Khashoggi death: key figures Jamal Khashoggi Washington Post journalist who was critical of the Saudi regime and the young Crown Prince Mohammed bin Salman, he was murdered on 2 October in the Saudi Arabian consulate in Istanbul AFP Jamal Khashoggi death: key figures Saudi Crown Prince Mohammed bin Salman Heir to the Saudi throne, Mohammed bin Salman has been implicated in the murder, with US officials claiming that he must have known of the plot AFP/Getty Jamal Khashoggi death: key figures 15 man hit squad Turkish police suspect these 15 men of being involved in the murder of Jamal Khashoggi, issued 10 October, 8 days after the journalist disappeared EPA Jamal Khashoggi death: key figures Saud al-Qahtani Aide to Crown Prince Mohammed bin Salman, Saud al-Qahtani is claimed to have ordered Khashoggi's murder Saud Al-Qahtani/Twitter Jamal Khashoggi death: key figures Maher Abdulaziz Mutreb A former diplomat who often travelled with the Crown Prince, Mutreb was initially claimed to be the leader of the hit squad and is pictured here entering the Saudi consulate on the day of the murder AP Jamal Khashoggi death: key figures Mustafa al-Madani First implicated in the 15 CCTV photos released by the Turkish police, al-Madani was later found to have been used as a body double for Khashoggi, leaving the Saudi consulate dressed in his clothes on the day the journalist was killed CNN Jamal Khashoggi death: key figures Salah bin Jamal Khashoggi (L) Son of the murdered journalist met with Crown Prince Mohammed bin Salman on 23 October EPA

He has also provided mixed messages about Saudi Arabia’s culpability over the murder, initially appearing to accept the royal family’s denials before describing the country’s handling of the case as the “worst cover-up in the history of cover-ups”.

Turkey is seeking the extradition of 18 suspects, including 15 members of the alleged Saudi hit squad sent to kill Mr Khashoggi, who lived in exile in the US and had written critically of Saudi Arabia's crown prince Mohammed bin Salman.

Some of those implicated are close to the prince, whose condemnation of the killing has failed to ease suspicions he was involved.

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In a video message to a memorial in Washington for the murdered journalist, Ms Cengiz urged Mr Trump to support Turkey’s request for Saudi Arabia to extradite those it has detained in connection with the killing.

"I would like him to support Turkey's efforts in trying to bring light to this situation and to discover the whereabouts of his body," Ms Cengiz said, adding: "Our pain is still as fresh as the first day."

On Thursday, US state department spokesman Robert Palladino told reporters Mr Khashoggi's remains should be located and returned for a proper burial.