President Donald Trump said he was "waiting to hear from" Saudi Arabia about the culprit in Saturday's drone attacks on two Saudi oil plants "and under what terms we would proceed!"

Many national-security experts said that made it look as if Trump was waiting on Saudi Arabia to make decisions affecting the US.

Rep. Tulsi Gabbard, who is running for the 2020 Democratic presidential nomination, said Trump was "having our country act as Saudi Arabia's b----."

US officials have accused Iran of being behind the drone attacks, which Iran has denied. Saudi Arabia has not blamed Iran.

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Rep. Tulsi Gabbard has described President Donald Trump's response to the drone attacks on two Saudi oil plants as "having our country act as Saudi Arabia's b----."

Gabbard was reacting to Trump's tweet on Sunday that the US was "waiting to hear from the Kingdom as to who they believe was the cause" of the attacks "and under what terms we would proceed!"

Gabbard, who is vying for the Democratic nomination in the 2020 presidential election, tweeted later: "Trump awaits instructions from his Saudi masters. Having our country act as Saudi Arabia's b---- is not 'America First.'"

Gabbard has attacked Trump's relationship with Saudi Arabia before, using a similar insult in November. Her policy platform includes ending the US's alliance with Saudi Arabia.

Gabbard's own Middle East policy has also been attacked, particularly her choice in 2017 to meet Syrian President Bashar Assad, a foe of Saudi Arabia who's been accused of war crimes.

Smoke seen following a drone attack and a fire at Saudi Aramco's factory in Abqaiq, Saudi Arabia, on Saturday. VIDEOS OBTAINED BY REUTERS/via REUTERS

US officials have blamed Iran for the drone attacks on two oil facilities belonging to the state-owned Saudi Aramco on Saturday morning.

The Iranian-backed arm of the Houthi rebels in Yemen has claimed that it, not Iran, is responsible for the attack. Iran has denied the US's accusations.

Many national-security experts also shared Gabbard's criticism.

Ben Rhodes, who was President Barack Obama's deputy national security adviser for strategic communications, tweeted on Sunday: "Just the President saying he will do whatever the Saudis want, including potentially going to war on their behalf."

Tamara Cofman Wittes, a senior fellow at Brookings Institution's Center for Middle East Policy, also said that Trump's tweet suggested that "we are now subcontracting our national security policy to the crown prince of Saudi Arabia," referring to the de facto ruler of the kingdom, Mohammed bin Salman.

The historian and Princeton University professor Kevin M. Kruse tweeted sarcastically: "As everyone knows, Article I of the US Constitution clearly states that the power to declare war is vested with the Kingdom of Saudi Arabia."

Trump has long touted his relationship with Saudi Arabia and Crown Prince Mohammed despite the crown prince's links to the murder of the Washington Post journalist Jamal Khashoggi.

Saudi Crown Prince Mohammed bin Salman with Trump. Pool/Getty Images

The drone attacks marked a new flare-up between US-Iran tensions. After US Secretary of State Mike Pompeo pointed the finger at Iran, Iran's foreign minister, Mohammed Javad Zarif, on Sunday accused his counterpart of "max deceit."

Read more: The world's oil producers keep a massive amount of capacity in reserve. But it's almost all in Saudi Arabia and the drone attack messed with that too.

Saudi Arabia has not blamed Iran for the attacks.

Saudi Aramco has shut down operations on roughly 5% of the world's daily production of crude oil and is reportedly considering delaying its long-awaited initial public offering. Oil prices have also surged by as much as 20%.