The statement was issued as Trump prepared to head to his golf resort in Florida for the Thanksgiving holiday and in the wake of the CIA’s conclusion that Saudi Crown Prince Mohammed bin Salman had ordered the October 2 killing of Khashoggi, a Washington Post contributor and US resident.

The nothing-to-see-here tone, the fractured syntax and falsehoods and the abundance of exclamation points were pure Trump – and as far from the massaged, nuanced products of past White Houses as one could imagine.

“It’s ‘America first’,” Trump told reporters on Tuesday before departing for Mar-a-Lago in Palm Beach, Florida. “For me, it’s all about ‘America first’. We’re not going to give up hundreds of billions of dollars in orders, and let Russia, China, and everybody else have them.”

Trump said Saudi Arabia had helped him keep oil prices down, and that without those efforts, “oil prices would go through the roof”.

As with US intelligence assessments that Russia interfered in the 2016 election to help Trump, he overrode his own advisers and downplayed their findings in favour of his own priorities and interpretation of events.

“King Salman and Crown Prince Mohammed bin Salman vigorously deny any knowledge of the planning or execution of the murder of Mr Khashoggi. Our intelligence agencies continue to assess all information, but it could very well be that the Crown Prince had knowledge of this tragic event – maybe he did and maybe he didn’t!” Trump wrote.

Trump’s clannish management style is also a factor in the Saudi decision. He has entrusted the relationship to his son-in-law, Jared Kushner, who has built a close partnership with MBS, as the young Saudi heir is known. Kushner has argued within the administration that the crown prince is crucial to assisting White House policy against Iran and in providing backing for a US-sponsored Mideast peace package expected soon.

Telling reporters later that there is no “definitive” proof, Trump washed his hands of the matter.

“I think that statement was pretty obvious, what I said,” Trump said, as reporters shouted questions above the din of the presidential helicopter blades. “I’m not going to destroy the world economy,” or harm US interests in the Middle East or elsewhere, over this case, he said.

The Trump administration has applied sanctions on 17 Saudis allegedly involved in the killing inside the Saudi consulate in Istanbul, but Trump appeared to be effectively writing off the possibility of larger consequences. Those might have included sanctions or a rebuke against the royal family, cancellation of weapons sales or a boycott.

“It’s a sign of weakness not to stand up to Saudi Arabia,” Republican Senator Rand Paul of Kentucky said in an interview. “Sometimes when you have two evils, maybe you don’t support either side.”

Republican Lindsey Graham, the South Carolina senator who is close to Trump, also disagreed with the president’s statement, saying America must not lose its “moral voice” on the international stage.

“It is not in our national security interests to look the other way when it comes to the brutal murder of Mr Jamal Khashoggi,” Graham said.

Likewise, Representative Adam Schiff, ranking Democrat on the House intelligence committee, said that to suggest that US silence can be bought with arms sales “undermines respect for the office of the presidency, the credibility of our intelligence community and America’s standing as a champion of human rights”.

Trump has also bucked convention and the advice of Cabinet and career government officials in pulling out of the Iran nuclear deal and the Paris climate accord, and in deploying punitive tariffs against allies and foes alike.

The president always places himself at the centre of events and decides what to do from that standpoint, said Ross Kennedy, an American history professor and presidential scholar at Illinois State University. In the case of Saudi Arabia, the kingdom’s lavish welcome in Riyadh for Trump in 2017 set the tone, Kennedy said.

Who should be Time Person of the Year? Trump can’t imagine anyone else but Trump

“He really personalises his interactions, not just with people in domestic audiences or in business, or with people he meets” at the White House, Kennedy said. “He does it with foreign leaders, and he bases much of what he does by how they treat him personally. The Saudis really laid it on thick.”

Past administrations, both Republican and Democratic, have prized a strategic partnership with Saudi Arabia and sometimes tempered criticism of human rights abuses that include religious persecution and the jailing of dissidents.

But President George W Bush also argued that US national security interests were served by defending human rights abroad, and his administration claimed to raise particular cases each time US officials met with leaders of Saudi Arabia, Egypt, Russia and other countries with poor human rights records.

On Iran, Riyadh has leveraged Trump’s opposition to the Iran nuclear deal reached under former president Barack Obama, appealing to Trump’s impulse to reverse his predecessor’s policies and giving Trump additional diplomatic footing to pull out of the deal, Kennedy said. Trump’s statement Tuesday begins with an indictment Iranian activities in the Middle East.

‘A simple equation’: Donald Trump says he stands by Saudis, despite Jamal Khashoggi’s killing, because of oil prices

Iranian Foreign Minister Mohammad Javad Zarif responded by mocking Trump on his English-language Twitter feed, including a reference to the US president’s false claim that Finland spends “a lot of time raking” its forests to prevent wildfires.

“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,” Zarif wrote. “Perhaps we’re also responsible for the California fires, because we didn’t help rake the forests – just like the Finns do?”

Secretary of State Mike Pompeo did not attempt to wrap the Saudi decision in diplomatic niceties.

“So, it’s a mean, nasty world out there, the Middle East in particular,” Pompeo said when asked whether the Trump administration is excusing murder. “The United States will continue to have a relationship with the Kingdom of Saudi Arabia. They are an important partner of ours. We will do that with the Kingdom of Saudi Arabia, its people. That is the commitment that the president made today. It’s that straightforward.”

Samantha Power, who was Obama’s ambassador to the United Nations, called the president’s statement an “abomination that will define the ignorance, corruption, cruelty and recklessness of this presidency for generations to come.”

And Senator Lindsey Graham, who has become a reliable Trump ally, took the president to task for letting the Saudis off easy.

“One thing I learned during the Obama years is that when you look the other way regarding problems in the Middle East, it seldom works out,” said Graham, who added that there is “strong bipartisan support” for serious sanctions against Saudi Arabia and members of the royal family.

Trump, fresh off the traditional pardoning of Thanksgiving turkeys at the White House, did not sound bothered about such criticism when he was asked who should be Time’s annual “Person of the Year”.

“That’s up to T ime Magazine,” Trump said, noting that he had “been there before”. Trump was named “Person of the Year” in 2016, but was runner-up last year.

“I can’t imagine anybody else other than Trump,” he added, referring to himself in the third person. “Can you imagine anybody other than Trump?”

Additional reporting by The Associated Press