US President Donald Trump has said Iran may be responsible for the Aramco attack, but he "certainly" wants to avoid a war with it.
Trump said the United States would help Saudi Arabia, but "the Saudis have to take the biggest responsibility in ensuring their security, including paying the money."
US Defense Secretary Mark Esper said recent attacks on two Saudi Aramco oil facilities were "unprecedented" and that the United States was working with its allies to defend a world order undermined by Iran.
Esper said on Twitter that he returned to the Defense Department after a meeting at the White House where the leadership of the Department and other officials briefed President Donald Trump on the situation.
Esber said he had spoken to Saudi Crown Prince Mohammed bin Salman and Iraq's defense minister. Esber told Riyadh that Washington was considering all options available to counter the attacks on Saudi Arabia, the official SPA news agency said.
The US ambassador to the United Nations, Kelly Kraft, said that the information available to Washington indicates that Iran is responsible for the attacks on Saudi oil installations.
She said during a Security Council session on Yemen that there was no evidence that the attacks were launched from Yemen, despite the Houthis claim responsibility.
Also in the context of US comments, Republican Senator Jim Rich, chairman of the Senate Foreign Relations Committee, attacked the Iranian government after the Aramco attacks, saying the attack underscored "Iran's efforts to instigate instability in the Middle East."
"Iran should not diminish US insistence. Any attack on US troops abroad would be overwhelmingly reactive, no targets would be ruled out," Reich warned in a statement of any possible attack on US forces.
The Wall Street Journal reported earlier Monday, citing US officials, that the United States had informed Saudi Arabia that Iran was the source of the latest attack on Aramco's factories.
In Riyadh, the Saudi Foreign Ministry said the kingdom would invite international experts, including from the United Nations, to participate in the investigation into the attack on Aramco's facilities and the world to condemn those responsible.
A preliminary investigation showed the use of Iranian weapons in the attack, which halted more than half of Saudi Arabia's oil production and damaged the world's largest refinery, a ministry statement said.
"The Kingdom strongly affirms that it is able to defend its territory and its people and respond strongly to these attacks."
The ministry said the attack was primarily aimed at world oil supplies, describing it as an extension of "previous hostile acts against Saudi Aramco's pumping stations using Iranian weapons" in May.
In contrast, Iranian President Hassan Rouhani said that Aramco's attack responded similarly from "Yemeni citizens" to the attack on their country.
"The Yemeni people have been exercising their legitimate right to defense," Rowhani told a news conference with his Russian and Turkish counterparts in Ankara. "The attacks were a reciprocal response to aggression against Yemen years ago."
The attacks on Saturday targeted two oil facilities, one of them a huge crude oil processing plant in Saudi Arabia, which led to a 5% drop in global oil production.