A top Senate Republican is blocking arms sales to Gulf Cooperation Council countries in order to pressure the Arab nations to resolve a brewing diplomatic crisis with Qatar.

Senate Foreign Relations Committee Chairman Bob Corker's decision, announced Monday, puts teeth into a series of statements from Secretary of State Rex Tillerson, who has repeatedly called for the Saudi-led bloc of Arab countries to end the diplomatic isolation of neighboring Qatar. The Saudis accuse Qatar of financing terrorism and aligning with Iran, but the dispute is an uncomfortable one for the United States, which has major military operations in Qatar.

"Before we provide any further clearances during the informal review period on sales of lethal military equipment to the GCC states, we need a better understanding of the path to resolve the current dispute and reunify the GCC," Corker, a Tennessee Republican, wrote in a letter to Tillerson.

In May, President Trump announced a $110 billion arms agreement with Saudi Arabia during his first foreign trip since taking office, a Middle Eastern tour focused on rallying support for a fight against terrorism and Iranian aggression. Trump then celebrated Saudi Arabia's ensuing efforts to cut diplomatic ties and impose a blockade on Qatar, offering the developments the first fruits of his foreign travel.

"So good to see the Saudi Arabia visit with the King and 50 countries already paying off," Trump wrote in a series of tweets. "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!"

Corker contradicted that idea directly, saying that Saudi Arabia's decision undercuts the purpose of Trump's visit. "I could not have been more pleased with the President's recent trip to Saudi Arabia," Corker wrote. "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."

Corker's announcement is just the latest indication that Trump's tweets did not reflect a consensus position among U.S. leaders. Tillerson, for instance, has put pressure on Saudi Arabia to ease the standoff even as Trump criticized Qatar. When that failed to occur, Tillerson's team accused the Saudis of using counterterrorism concerns as a pretext for settling "long-simmering disputes" with Qatar. And he implied that some of the demands made by the Saudi-led bloc as a condition for ending the crisis are not reasonable.

"While some of the elements will be very difficult for Qatar to meet, there are significant areas which provide a basis for ongoing dialogue leading to resolution," Tillerson said Sunday. "We believe our allies and partners are stronger when they are working together towards one goal which we all agree is stopping terrorism and countering extremism Each country involved has something to contribute to that effort. A lowering of rhetoric would also help ease the tension."

Under the U.S. arms sales process, the administration must notify Congress 30 days before the executive branch can sign government-to-government sales of military equipment. Corker's block imperils at least a portion of the $110 billion deal to Saudi Arabia, since about 20 percent of the deal was already finalized under the Obama administration.

The GCC countries are Saudi Arabia, Kuwait, the United Arab Emirates, Qatar, Bahrain and Oman.