Senators have demanded that Donald Trump investigate what role, if any, Saudi crown prince Mohammed bin Salman played in the murder of journalist Jamal Khashoggi.

Two senior senators invoked the Magnitsky Act in an attempt to force the president to determine whether the prince was involved in the Washington Post columnist’s death at the Saudi consulate in Istanbul.

The law, named after slain Russian tax lawyer Sergei Magnitsky, allows the US government to impose sanctions against a foreign person determined to have been responsible for human rights violations.

Bob Menendez, a Democrat, wrote to Mr Trump alongside Republican Bob Corker in an update to a 10 October demand for a sanctions determination. “Unprecedented times call for unprecedented measures,” Mr Menendez tweeted. The senators said they expected Mr Trump to make his determination within the 120-day deadline triggered last month.

“In light of recent developments, including the Saudi government’s acknowledgement that Saudi officials killed Mr Khashoggi in its Istanbul consulate, we request that your determination specifically address whether crown prince Mohammed bin Salman is responsible,” the pair wrote.

While Mr Trump has denounced Khashoggi’s killing as “an unacceptable and horrible crime” he has also made clear he does not want to punish Saudi Arabia for it.

Following a series of shifting denials, Riyadh eventually admitted Saudi operatives intentionally killed the columnist, but has insisted the Crown Prince was not involved.

Mr Trump has rejected calls by many in Congress, including members of his own party, for a tough response, and dismissed reports from US intelligence agencies that the crown prince must have at least known about such an audacious and intricate plot. “Maybe he did and maybe he didn’t!”, the president said in a statement.

He has suggested that the kingdom’s spending power and its opposition to Iran are his main concerns. He said in a statement laden with exclamation points and beginning with his trademark phrase “America First!” that Riyadh planned to invest some $450bn (£350bn) in the US thanks to his diplomatic efforts.

“It will create hundreds of thousands of jobs, tremendous economic development, and much additional wealth,” he said on Tuesday, giving top billing to purchases of military equipment from big guns Boeing, Raytheon and Lockheed Martin.

Mr Trump told reporters at the White House that oil prices would “skyrocket” if the US broke with the Saudis, and he was not going to “destroy” the world’s economy by being “foolish”.

He also praised the kingdom as “a great ally in our very important fight against Iran”.

The US has previously sanctioned 17 Saudi officials suspected of being responsible for or complicit in the 2 October killing of Mr Khashoggi, but members of Congress have called for harsher actions, including cancelling arms sales.

Mr Trump said “foolishly cancelling these contracts” would merely benefit Russia and China, which would be next in line to supply the weapons.

Asked by a reporter on Tuesday if he was saying that human rights were too expensive to fight for, he said: ”No, I’m not saying that at all.”

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

Mr Menendez tweeted a direct criticism of the president’s reasoning after sending his letter. He said: “The fact is we cannot allow exaggerated profits from weapons sales and other business deals to drive our foreign policy at the expense of our broader interests, human rights, and promoting values that will make us secure over the long-term.

“We know countries that observe democracy and human rights are less likely to go to war, less likely to draw American troops into battle, and better for global stability. In other words, when we stand up for democracy and human rights, we ARE putting America First.”

Mr Corker tweeted that “‘Maybe he did and maybe he didn’t’ won’t cut it”. He added: “I never thought I’d see the day a White House would moonlight as a public relations firm for the crown prince of Saudi Arabia.”

Turkey’s foreign minister also appeared to rebuke Mr Trump during a trip to Washington, saying Khashoggi’s slaying should not be covered up for the sake of maintaining trade ties with Riyadh..

Mevlut Cavusoglu also told Turkish journalists that Saudi Arabia’s cooperation over the investigation into the killing is not “at the desired level”. He added that Turkey would take formal steps to seek an international investigation if it reaches an “impasse” with Riyadh.

He added: “This is a humanitarian issue. It concerns a murder. It is not possible to say ‘our trade will increase, let’s cover this up, let’s ignore it’.”

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Iran’s foreign minister mocked the president's announcement that he did not intend to punish the Saudi leadership. In a tweet sent late on Tuesday, Mohammad Javad Zarif noted that Mr Trump “bizarrely devotes the FIRST paragraph of his shameful statement on Saudi atrocities to accuse IRAN of every sort of malfeasance he can think of”.

He went on to joke that “perhaps we’re also responsible for the California fires, because we didn’t help rake the forests - just like the Finns do?”

Mr Trump has said he plans to meet with Mr bin Salman at the G20 summit in Argentina in December.