(CNN) Senate Foreign Relations Chairman Bob Corker sent a letter to Secretary of State Rex Tillerson on Monday saying he will block foreign military sales to members of the Gulf Cooperation Council until they can resolve their dispute with Qatar.
Saudi Arabia, the United Arab Emirates, Bahrain and Egypt cut ties with Qatar on June 5, accusing the country of supporting terrorism and destabilizing the region.
As chairman of the Foreign Relations Committee, Corker has a unique perch in Congress to try to force the countries to a resolution because the top Republican and Democrat on the respective House and Senate committees informally sign off on arms deals before they are formally notified to Congress. The full body then votes approve or disapprove of the sale.
Under the foreign arms sale process with the Pentagon and State Department, if any one of those four lawmakers disapproves of a sale, it does not move forward to be formally notified to Congress.
"I could not have been more pleased with (President Donald Trump's) recent trip to Saudi Arabia. The unity of the Gulf States and their commitment to security cooperation were welcome steps forward," Corker wrote in the letter to Tillerson.
"Unfortunately, the GCC did not take advantage of the summit and instead chose to devolve into conflict. All countries in the region need to do more to combat terrorism, but recent disputes among the GCC countries only serve to hurt efforts to fight ISIS and counter Iran," the Tennessee Republican added.
Congress has never voted in favor of stopping a foreign military sale that's been formally notified -- the latest attempt was a close 47-53 vote that failed to block a $500 million sale to Saudi Arabia -- but the committee leaders have been able to play a role in stopping or delaying arms sales.
If Corker does not sign off on deals for the foreseeable future, it could hamper Trump's $110 billion arms sale with the Saudis, most of which still has to be agreed to and run through the congressional process.
Still, the White House on Monday described Corker's call as constructive.
"I think we share Senator Corker's goal on two fronts," White House press secretary Sean Spicer said. "One, obviously we want to resolve the situation. I know that the states that are involved are viewing this as a family matter, and Secretary Tillerson is helping to facilitate some of the that. We believe that is positive. We share that concern. We also share the concern about terror financing that Senator Corker has, and I think we can work together on both those goals."
Corker's opposition includes all six members of the Gulf Cooperation Council -- the five countries involved in the Qatar dispute as well as Kuwait, which has been acting as a mediator.
Last week, Saudi Arabia, the UAE, Bahrain and Egypt sent Qatar a list of 13 demands, including shutting down the Qatari-owned Al Jazeera network.
The four Arab states gave Qatar 10 days to comply with the demands. Qatar said it is studying the list.
A State Department official issued a statement to CNN: "As a matter of policy, we do not comment or confirm the status of proposed defense sales until they are formally notified to Congress" and referred to Tillerson's Sunday statement in which he encouraged Qatar and the other countries involved in the dispute to meet to resolve the crisis.