President Donald Trump says the United States is “locked and loaded” after the destructive aerial attack on Saudi Arabia’s oil installations, which have reduced world supplies by more than 5.5 million barrels per day.

However, the U.S. president underlined in a tweet that Washington is waiting for “verification” as to who was responsible and to hear from “the Kingdom as to who they believe was the cause of the attack”.

Trump also announced he has authorized release of oil from strategic reserves to stabilize world oil prices. Saudi Arabia has also said it will make up any shortages by releasing oil from its own reserves, kept at different locations around the globe.

In another tweet, Trump changed his position regarding his willingness to talk with Iranians without preconditions. "The Fake News is saying that I am willing to meet with Iran, 'No Conditions.' That is an incorrect statement (as usual!)."

Early indication on Monday show significant spike in oil prices of under 10 percent, but it is too early to say oil prices will significantly rise. Saudi Arabia is the largest OPEC producer and was a “swing producer” until the attack, meaning it had the capability of both boosting output or cutting back to affect prices.

Yemen’s Iran-backed Houthi forces took responsibility for the September 14 drone strikes, but U.S. Secretary of State Mike Pompeo announced hours after the attack that there was no indication it came from Yemen, and directly blamed Iran.

Analysts and experts have also expressed doubt such an attack would have been possible from Yemen, considering the distances involved and Saudi air defenses guarding the border regions.

Iran has denied the accusations and argued Saudi Arabia has been involved in a bloody war in Yemen and this kind of incidents are related to the that conflict. At the same time, a commander of Iran’s revolutionary Guards has repeated a warning that U.S. forces in the region are within range of Iranian missiles.