Tensions between the White House and the State Department over how to approach the ongoing dispute between the United States’ Gulf allies are reaching a boiling point, due to what the White House sees as Secretary of State Rex Tillerson’s stalling of large arms-sales packages President Trump agreed to in May.

For months, huge parts of arms-sales packages Trump announced during his trip to the region, including more than $110 billion worth for Saudi Arabia, have languished. While some are being held up by Congress, Trump and his White House team are increasingly frustrated by Tillerson’s State Department, which has also been slow-walking the deals as part of Tillerson’s quest for leverage as he tries to mediate the Arab family feud, four senior administration officials told me, speaking on the condition of anonymity in order to discuss internal administration dealings.

“There are sales that are sitting on the desk of the secretary of state,” one senior White House official said. “People in the White House are trying to organize their response to force State to do what they should have done all along.”

White House officials argue that the stalling of the arms sales is simply not effective in pressuring Saudi Arabia to make concessions to Qatar. Moreover, they say, the delays are holding up thousands of jobs in the U.S. defense industry and undermining America’s credibility as a reliable supplier of defense weapons.

For Trump, it’s largely about the fact that he gave his word on the deals and now White House officials see his own secretary of state as going back on that word. The president is personally upset with the lack of progress on the arms-sales deals, another senior White House official said.

“These were commitments made by the president,” the official said. “He keeps asking about it, and we don’t know what to tell him.”

The weapons packages altogether represent the largest ever set of arms sales by the United States, but are actually a conglomeration of several sets of weapons sales, with various different circumstances. A large portion of the sales announced in Riyadh were based on deals struck during the Obama administration or sales that were already in the pipeline.

Immediately after the May summit, the State Department and Congress did approve some new sales, including the controversial sale of F-16 fighter planes to Bahrain. But in late June, Senate Foreign Relations Committee Chairman Bob Corker (R-Tenn.) wrote to Tillerson that he would not approve any further sales of lethal weapons to Gulf allies until there was more clarity about the path to resolving the crisis.

The White House believes that Tillerson and Corker are working together to stall the deals. “They both blame each other behind the scenes,” one White House official said. Sources confirmed that Tillerson was aware in advance of Corker’s letter to hold up the arms deals, expressed support and indicated that it would be helpful to increase his diplomatic leverage.

Trump and Corker spoke about the issue Sept. 15, a Corker aide told me, but Corker’s position hasn’t changed.

“Senator Corker will again begin providing informal clearance on future sales when there is a path forward to resolve the dispute and sees this as a tool for additional administration leverage,” the aide said.

White House officials are also upset with Corker but see Tillerson as the main obstacle. White House officials said Tillerson is personally holding up some of the larger items, such as the sale of THAAD missile defense systems to Saudi Arabia.

Ever since the Gulf crisis began, Tillerson and Corker have taken a different position than the White House, seeking to pressure Saudi Arabia and other parties to negotiate a end to their blockade of Qatar.

Trump has repeatedly criticized Qatar and expressed support for Saudi Arabia. Senior White House adviser Jared Kushner, who was instrumental in arranging the arms-sales deals before the Riyadh summit, has cultivated close ties to the Saudi leadership, especially the new crown prince, Mohammed bin Salman.

“In Trump’s and Jared’s minds, everything is underwritten by Saudi leadership. Everything goes through the Saudis, and the Qataris need to get in line,” said Andrew Bowen, visiting scholar on the Middle East at the American Enterprise Institute.

Tillerson has been attempting to mediate between the parties but is concerned that the White House’s actions undermine his efforts to strike a balanced position. For example, after Kushner traveled to several Gulf countries last month, Tillerson called each of those countries’ foreign ministers to make sure that Kushner had not sent conflicting messages about U.S. policy regarding the crisis, a senior State Department official told me.

Tillerson’s spokesman R.C. Hammond told me the president and Tillerson are having “an ongoing conversation” about how the United States can help guide the GCC to resolve its conflict. “One outcome of this collaboration has been the President’s recent call for a resolution,” he said. “Both understand how other points of pressure will be used to encourage a prompt solution.”

Experts said Saudi Arabia and other Gulf states are relying on the White House to rein in Tillerson and are therefore resisting his attempts to bring any pressure to bear on them.

“When you get mixed messages from the U.S., the tendency is to look towards the White House,” said Brian Katulis, senior fellow at the Center for American Progress. “Other countries in the world and our key partners see this up close and personal and they choose to ignore what they don’t want to hear, which is Tillerson’s message.”

The dispute is part of a growing overall unhappiness in the White House with Tillerson, who is increasingly isolated inside the administration. Administration officials don’t believe Tillerson will leave his post soon, but there’s increasing talk of promoting U.S. Ambassador to the United Nations Nikki Haley to lead the State Department if he does resign.

Yesterday, on the sidelines of the U.N. General Assembly, Trump met with the Qatari emir, Sheikh Tamim Bin Hamad al-Thani, and said about the Gulf crisis: “I have a very strong feeling that it will be solved pretty quickly.”

The longer it drags on, the worse will be the consequences not just for the countries of the region but also for the relationship between the U.S. president and his secretary of state.