WASHINGTON ― The Pentagon was set to outline new military options to President Donald Trump on Friday to respond to an attack on Saudi Arabia’s oil industry, but Riyadh still has an unpaid bill with the Pentagon for $181 million over assistance in Yemen.

Despite the Trump administration’s emphasis on the U.S.-Saudi alliance in the wake of an attack that both sides attribute to Iran, Saudi Arabia has not repaid the Pentagon for its midair refueling assistance for its bombing runs over Yemen, nine months after the Pentagon announced it would seek to recoup its costs.

Amid questions about whether it was the responsibility of the Saudis to defend themselves, Trump ― known for his perennial focus on burden-sharing in security arrangements ― told reporters on Monday that Saudi Arabia would play a large role. He emphasized that Riyadh has been a “great ally” for its investments in the U.S., saying: "Saudi Arabia pays cash.”

Trump told reporters at the White House on Friday that as the U.S. builds a regional coalition to face Iran, America will not shoulder the costs by itself. “We’re also working on the cost of this whole endeavor, and Saudi Arabia has been very generous,” Trump said.

The unpaid bill for refueling contrasts with those comments, and it is already inflaming U.S. lawmakers, many of whom are frustrated with Riyadh’s alleged involvement in the murder of journalist Jamal Khashoggi and the Yemen war’s civilian toll.

“Saudi failure to reimburse us for aircraft refueling — hundreds of millions in taxpayer dollars — involves both deep insult and costly injury. It is entirely unacceptable that the Saudis have not reimbursed the Department of Defense for hundreds of millions in refueling costs," Sen. Richard Blumenthal, D-Conn., said in a statement. “The American taxpayer-funded U.S. Department of Defense is not the Saudi Royal Family’s piggy bank.”

Inquiries from Blumenthal and Senate Armed Services Committee ranking member Jack Reed, D-R.I., prompted the Pentagon to announce in December that it would seek to recoup the money it failed to charge the United Arab Emirates and Saudi Arabia for aid for the midair refueling ― which Riyadh ended in 2018.

The original balance due was since revised from $331 million to $291 million, and the Pentagon has separately recouped $118 million from the UAE, but Saudi Arabia has not repaid the United States, according to congressional sources. Blumenthal is pressing for language in the annual defense policy bill to require the Pentagon regularly update Congress on the matter.

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It’s unclear why Saudi Arabia has not made the payments. The Saudi Embassy in Washington did not immediately respond to a request for comment.

Pentagon spokeswoman Cmdr. Rebecca Rebarich declined to provide the specifics of its collection efforts on Thursday, but confirmed that "the process of reimbursement is continuing, and we continue to expect full reimbursement of refueling expenses.”

Becca Wasser, a senior policy analyst at the think tank Rand, said Saudi Arabia has an interest in being on Congress’ good side, especially as it may seek to buy American counter-drone weapons or augment its arsenal of Patriot missile defense systems, which are produced by American defense contractor Raytheon.

“Saudi Arabia learned about the importance of the U.S. Congress the hard way, as a result of the war in Yemen and the murder of Jamal Khashoggi,” Wasser said. “With Saudi Arabia at risk of future attacks, they would want to make sure they don’t have any issues looming over their military relationships.

“You don’t want to want to have a bill with the Department of Defense at the same time you are asking for additional things from the Department of Defense.”

Trump was scheduled to have a meeting Friday to consider a list of potential airstrike targets inside Iran, according to U.S. officials familiar with the planned discussions. He will also be warned that military action against the Islamic Republic could escalate into war, the U.S. officials told The Associated Press. Iran has denied involvement in the attack on Saudi oil infrastructure and warned the U.S. that any attack on it will spark an “all-out war” with immediate retaliation.

Critics in Congress says the president should not lead the country into an unnecessary conflict with Iran to protect Saudi Arabian oil. Tim Kaine, D-Va., a member of the Senate Foreign Relations and Armed Services committees, pledged to file a war powers resolution to force a Senate vote to immediately end any such military action.

The Pentagon said the U.S. military is working with Saudi Arabia to find ways to better protect the northern part of the country. Meanwhile, a forensic team from U.S. Central Command is pouring over cruise missile and drone debris in search of hard evidence that the strikes came from Iran, but the Pentagon said the assessment is not complete.