This story has been updated with comments from Boeing spokeswoman Caroline Hutcheson.
WASHINGTON — U.S. President Donald Trump sided with Saudi Arabia and other Arab countries Tuesday in a deepening diplomatic crisis with Qatar, casting a cloud over a $21.1 billion sale Boeing is counting on to keep open its F-15 production line.
Trump's sharp criticism for Qatar comes at a delicate time for the sale, which includes as many as 72 F-15QA multirole fighter aircraft. President Obama approved the long-delayed sale in November in a bid to bolster Sunni allies against Shiite rival Iran, but the U.S. and Qatar have not yet finalized it.
It's also unclear how Trump's broadside would affect the U.S. military presence in Qatar. Al Udeid Air Base, outside Doha, is the nerve center of the U.S. fight against the Islamic State and home to 10,000 U.S. personnel. On Tuesday, U.S. officials continued to insist the clash would not force the U.S. to scale back its operations.
Several U.S. senators downplayed the risk to the F-15 sale, and it may be too soon to tell. Democratic Sen. Claire McCaskill, whose home state Missouri produces the F-15 and F-18, said she hoped the crisis would not derail it. The sale, years in the making, has been billed as extending Boeing's struggling F-15 production line into the 2020s.
"I can't imagine that the president would want to have that kind of impact on American jobs," McCaskill said. "I know that what [arms sales] he announced in Saudi Arabia, a lot of those are going to be built not in America, but over there."
The U.S. forwarded Qatar a letter of offer and acceptance for the fighter jets, related spare parts, logistical support and munitions. But Qatar has not signed the letter — which is the government-to-government agreement formalizing the sale — according sources with knowledge of the deal.
Trump, in a series of early-morning tweets on Tuesday, appeared to endorse the accusation the oil-rich Gulf nation is funding terrorist groups. Trump said he'd stated during his trip that funding of "Radical Ideology" can't be tolerated, and added, "Leaders pointed to Qatar — look!"
"They said they would take a hard line on funding ... extremism, and all reference was pointing to Qatar. Perhaps this will be the beginning of the end to the horror of terrorism!" Trump said, arguing that his visit to Saudi Arabia was "already paying off." Qatar denies supporting extremism.
The president's critique of Qatar inserted Washington directly into the crisis that has pitted the tiny country against Saudi Arabia, Bahrain, Egypt and the United Arab Emirates. Those countries announced Monday they were cutting diplomatic ties with Qatar, a move that ricocheted across the region as airlines suspended flights, ports closed to Qatari ships and anxious residents started stockpiling food.
Qatar's neighbors have long accused the country of tolerating or even encouraging support for extremist groups, including al-Qaida's branch in Syria, formerly called the Nusra Front. Those nations have also objected to Qatari support for Islamist groups such as the Muslim Brotherhood in Egypt, whose political ideology challenges the system of hereditary rule in Saudi Arabia, the UAE and other nations.
Trump's tweets appeared in stark contrast to Secretary of State Rex Tillerson's call on Monday for Gulf Cooperation Council countries to "remain unified and that parties sit down together and address their differences," with an offer to help mediate the differences.
"The United States' relationship with Qatar is strong and we cooperate with Qatar in a number of areas, including in the fight against terror," a State Department official said in a statement on Tuesday. "The United States and the Coalition [against ISIS] are grateful to the Qataris for their longstanding support of our presence and their enduring commitment to regional security. All of our partnerships in the Gulf are incredibly important and we count on the parties to find a way to resolve their differences sooner rather than later."
After a reporter showed Senate Foreign Relations Committee Chairman Bob Corker, R-Tenn., Trump's Qatar tweets on Tuesday, Corker declined to comment on them directly and also voiced support for U.S. alliances with Gulf states.
"It's best to continue to work with each of them and their differing sensibilities, and build on the strengths they have to offer us as we deal with the region," Corker said. "I try not to divide a group off. In everything I do, I try not to do that."
Corker noted he was among lawmakers who pushed the Obama administration to complete the Qatar F-15 sale and said his feelings on it were unchanged.
The Senate Foreign Relations Committee's top Democrat, Sen. Ben Cardin, of Maryland, did not anticipate the arms sale would be derailed. He suggested the U.S. has differences with other Middle Eastern allies and should not single out Qatar.
"The more unity we can have in the war against terror, the better it is, but we have to recognize we have disagreements with all these countries," Cardin said.
The Senate Armed Services Committee's top Democrat, Sen. Jack Reed, of Rhode Island, said he had no immediate sense the sale would be jeopardized, but felt the crisis overall will add a new dimension for future sales. SASC chairman John McCain, R-Ariz., said the issue deserved careful study.
A week ago, Boeing CEO Dennis Muilenberg said in public remarks about the Qatar deal and other international sales that he could see "the F-15 line being extended in a strong way well into the next decade."
Loren Thompson, an analyst with the Lexington Institute with close ties to Boeing, said he believed the F-15 deal would proceed, once the Qatari government sees it created the problem. President Trump is eager to show progress against the Islamic State and Iran — and likely does not want to impede the arms sale.
"The outcome is simple," Thompson said. "Qatar will clean up it's act, and the deal will go forward."
Valerie Insinna and The Associated Press contributed to this report.
Joe Gould was the senior Pentagon reporter for Defense News, covering the intersection of national security policy, politics and the defense industry. He had previously served as Congress reporter.