Saudi Arabia has rejected US accusations of aligning itself with Russia amid the Ukraine war by making oil production cuts to drive up crude prices, insisting it was purely a business decision.

"We are astonished by the accusations that the kingdom is standing with Russia in its war with Ukraine," the Saudi defence minister, Prince Khaled bin Salman, tweeted late Sunday.

The Saudi-led OPEC+ cartel -- which includes Russia -- has angered Washington by deciding to cut production by two million barrels per day from November, adding further pressure on soaring crude prices.

"It is telling that these false accusations did not come from the Ukrainian government," Prince Khaled wrote.

"Although the OPEC+ decision, which was taken unanimously, was due to purely economic reasons, some accused the kingdom of standing with Russia.

"Iran is also a member of OPEC, does this mean that the kingdom is standing with Iran as well?" he asked, referring to Saudi Arabia's regional rival.

In a speech broadcast on Sunday night, Saudi King Salman bin Abdulaziz Al Saud insisted his country was "working hard, within its energy strategy, to support the stability and balance of global oil markets".

- Re-evaluation -
 

Appearing on CNN on Monday, Fahad Nazer, spokesman for the Saudi embassy in Washington, similarly stressed that the OPEC+ move was "determined strictly by market fundamentals".

He also emphasised the importance of US-Saudi ties, noting that the two countries cooperated in repelling Iraqi dictator Saddam Hussein's 1990 invasion of Kuwait, and more recently in fighting against the jihadist Islamic State group.

"If that's not the definition of an alliance, I don't know what is. We certainly consider the United States to be our strongest partner. It has been for the past 80 years," Nazer said.

"And it is by far our most important strategic partnership. And we certainly look forward to continue well into the future."

The United Arab Emirates and Bahrain, which like Saudi Arabia are US partners as well as OPEC members, also defended the cartel's decision Sunday as a "technical" move.

White House spokesman John Kirby said last week that Riyadh knew the cut "would increase Russian revenues and blunt the effectiveness of sanctions" on Moscow.

The United States has vowed to re-evaluate ties with the oil-rich kingdom since the cut, which was seen as a diplomatic slap in the face for President Joe Biden by hiking prices on US consumers weeks before congressional elections.

Despite vowing to make the kingdom an international "pariah" following the October 2018 murder of journalist Jamal Khashoggi, Biden travelled to Saudi Arabia in July and met with Crown Prince Mohammed bin Salman -- with the two greeting each other with a high-profile fist bump.

But with relations now strained, US National Security Advisor Jake Sullivan said Sunday that Biden has "no plans" to meet with Prince Mohammed at an upcoming G20 summit in Indonesia.