TEHRAN (Press Shia) – A US envoy tasked with resolving the diplomatic crisis between Qatar and its Persian Gulf Arab neighbors has quit his post citing "unwillingness" of regional leaders to engage in dialogue.

– World news –

Anthony Zinni, a retired Marine general, resigned after realizing he "could not help resolve" the 18-month-long dispute, in which four Arab countries cut diplomatic and transport ties with Qatar, CBS News Television Network reported.

Saudi Arabia, the United Arab Emirates, Bahrain and Egypt all cut off diplomatic ties with Qatar on June 5 2017, after officially accusing it of “sponsoring terrorism.”

The quartet also imposed a land, sea and air blockade on the small Persian Gulf state.

Zinni, a former commander of the US Central Command, said he was stepping down because of the "unwillingness of regional leaders to agree to a viable mediation effort that we offered to conduct or assist in implementing."

A spokesperson for the US State Department confirmed Zinni's resignation.

Robert Palladino said US President Donald Trump's administration will continue to pursue Zinni's work, which also included discussing with regional leaders the idea of a so-called NATO-like group called the Middle East Strategic Alliance (MESA).

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 Persian Gulf neighbors.

The sources claim Zinni did not depart because of bad blood with other administration officials.

Zinni was appointed by former Secretary of State Rex Tillerson in August 2017, two months after the dispute between the Saudi-led quarter and Qatar erupted.

His resignation coincided with a Middle East tour by Secretary of State Mike Pompeo that includes stops in the six countries that form the Persian Gulf Cooperation Council (PGCC), as well as Egypt and Jordan.