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© REUTERS/Mike Blake
US President Donald Trump says Washington has "a reason to believe" it knows the mastermind behind the drone strikes on the Saudi oil refineries and is poised to respond pending confirmation from Riyadh.

"Saudi Arabia oil supply was attacked. There is reason to believe that we know the culprit, are locked and loaded depending on verification, but are waiting to hear from the Kingdom as to who they believe was the cause of this attack, and under what terms we would proceed!" Trump tweeted Sunday.

Although the attacks on the two Saudi oil facilities were claimed by the Houthi rebels, Washington immediately pointed the finger at Tehran, claiming that the attack was too complex and too devastating to be coordinated by the rebels. A senior official told Reuters that US intelligence believes the attack originated from the direction of Iraq and Iran, rather than from the area controlled by the Houthis.

Trump's announcement comes shortly after he greenlighted the release of emergency petroleum reserves "if needed," to offset the 50-percent drop in production by Saudi Aramco, whose largest Abqaiq oil processing plant was crippled as result of the Saturday morning attacks.

Riyadh has so far not named a perpetrator, calling the drone strikes "terrorist attacks" aimed at disrupting the global oil supply. Tehran has dismissed the allegations of its involvement, calling the US claims "maximum lies" and saying that it is ready to protect itself if war breaks out.

Earlier this week, Trump said he would have "no problem" in meeting Iranian President Hassan Rouhani on the sidelines of the UN General Assembly. US Secretary of State Mike Pompeo told reporters on Tuesday that "the President has made very clear he is prepared to meet with no preconditions."

However, on Sunday, Trump appeared to have contradicted his own top diplomat, denouncing reports that he is willing to meet with Iran with "no conditions" as "fake news."