(CNN) Retired General Anthony Zinni, the Trump administration's envoy working to resolve the Gulf region's diplomatic dispute, has resigned from his role at the State Department.

Two State Department officials told CNN that Zinni left because he felt he had reached a dead-end, believing there was no forward movement on resolving the stalemate between Qatar and its Gulf neighbors. The sources claim Zinni did not depart because of bad blood with other administration officials. Zinni confirmed in an email to CNN that the sources' characterizations of his departure were correct.

"I did not think my services were needed," he said.

Gulf nations, including Saudi Arabia, the United Arab Emirates, Egypt, Bahrain and Yemen, severed ties with Qatar in 2017 over its alleged support for terrorist organizations such as the Muslim Brotherhood. Former Secretary of State Rex Tillerson announced in early August 2017 that Zinni would travel to the region, telling the press that the US was "committed to see this disagreement resolved, restore Gulf unity, because we think it's important to the long-term effort to defeat terrorism in the region."

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