Democrats on Capitol Hill have suggested transferring US weapons systems in Saudi Arabia to Ukraine and suspending a planned transfer of Patriot missiles to Riyadh in the wake of what they call a “turning point” in Washington’s relationship with the kingdom.

Ro Khanna, a Democratic congressman from California who is a leading supporter of a weapons freeze, said he believed that “at the very least” Congress would move to halt the transfer of Patriot missiles to the kingdom, and probably pause other defense initiatives.

Khanna is a longtime critic of Saudi Arabia and was one of the original sponsors of a 2019 measure that received bipartisan support and would have forced the US to end military involvement in Saudi Arabia’s war in Yemen. That resolution was vetoed by then-president Donald Trump.

In an interview with the Guardian, Khanna said tensions had reached a boiling point that was comparable to US sentiment following the murder of the Washington Post journalist Jamal Khashoggi.

The break in the relationship followed an announcement last week that Opec+, the oil cartel, had agreed to cut oil production by 2m barrels a day over the strong objections of, and lobbying by, the administration of Joe Biden. The move was seen as both a boost to Vladimir Putin and his war effort in Ukraine, and a stunning betrayal of Saudi Arabia’s relationship with the US, just weeks after the president had visited Crown Prince Mohammed bin Salman in Jeddah.

“I think President Biden is judicious and pragmatic by temperament but this was a real slap in his face,” Khanna said. While lawmakers like him have long advocated for a tougher response to Saudi on human rights grounds, Khanna said the Opec+ move had galvanized members across Congress.

“This is a second moment like Khashoggi’s murder. I believe it is a total miscalculation by the Saudis,” he said, adding that there was still time for the kingdom to change course.

Pressed on whether Democrats were likely to move beyond rhetoric, Khanna pointed to recent comments by his colleague Robert Menendez, a Democratic senator who as chairman of the foreign relations committee said he was prepared to halt Saudi weapons sales.

“At the very least, the Patriot missiles will be suspended,” he said. “The fact that Menendez has spoken out means that at a minimum it is going to happen.”

Meanwhile, Chris Murphy, an influential Democratic senator from Connecticut, said he believed the US ought to suspend the sale of advanced air-to-air missiles to Saudi Arabia and repurpose these missiles to Ukraine.

“For several years, the US military had deployed Patriot missile defense batteries to Saudi Arabia to help defend oil infrastructure against missile and drone attacks. These advanced air and missile defense systems should be redeployed to bolster the defenses of eastern flank Nato allies like Poland and Romania – or transferred to our Ukrainian partners,” Murphy said in a statement.

While physically transferring existing weapons systems in Saudi Arabia to Ukraine would not be particularly complicated logistically, experts said it could risk accusations that the Biden administration was escalating its support for Ukraine beyond levels that it considered appropriate, because the systems might require on-the-ground US personnel for support.

William Hartung, a senior research fellow at the Quincy Institute, said at a minimum, any such move to shift weapons would be met by serious debates within the White House and Congress. At the same time, he said, Russia’s continuing assault on Ukraine meant that “political considerations are shifting”.

Changes to planned deliveries of Patriot missiles would probably cause “consternation” in Saudi Arabia, but changes to delivery of spare parts and maintenance could ground large parts of the Saudi air force, he said.

Hartung said he believed the Saudis might be underestimating the impact of the sudden break in relations with Washington, given the relationship appeared to survive the Khashoggi murder. In that case, however, Trump was in the White House and steadfastly loyal to the Saudis. Hartung said he believed it was unlikely that Biden would veto a congressional resolution aimed at the kingdom, as Trump did in 2019.

“It’s not a done deal, but the political tides are stronger against the Saudis than they have been – possibly ever,” he said.

The Saudi foreign ministry this week rejected the criticism of its Opec+ decision and insisted the cartel had acted with unanimity and in its own economic interest. It also rejected any assumption that it could be forced into a policy U-turn.

“The kingdom stresses that while it strives to preserve the strength of its relations with all friendly countries, it affirms its rejection of any dictates, actions, or efforts to distort its noble objectives to protect the global economy from oil market volatility,” it said.

Khanna hit back at that claim.

“The reality is that there is no economic case for what they are doing. This was punitive for Americans and it is aiding Putin,” he said.

A spokesperson for the national security council said Opec’s decision last week to “align its energy policy with Russia’s war and against Americans” underscored Biden’s earlier call to set a “different sort of relationship” with Saudi Arabia.

“We are reviewing where we are, we’ll be watching closely over the coming weeks and months, consulting with allies, with Congress – and decisions will be made in a deliberate way,” the spokesperson said.