U.S. Secretary of State Rex Tillerson (R) escorts Qatari Foreign Minister Sheikh Mohammed Bin Abdulrahman Al Thani (L) prior to a scheduled meeting at the State Department June 27, 2017 in Washington, DC.

:: US Secretary of State Rex Tillerson has departed for Qatar as he tries to mediate a dispute between the energy-rich country and a quartet of Arab nations.

Tillerson left Kuwait City and was due to arrive in the Qatari capital, Doha, before noon on Tuesday. He has held talks Kuwait’s ruling emir, Sheikh Sabah Al Ahmed Al Sabah, after arriving in Kuwait on Monday.

Sheikh Sabah has been acting as a mediator between Qatar and four states lined up against it: Saudi Arabia, Bahrain, the United Arab Emirates and Egypt.

The four countries broke diplomatic relations with Qatar last month and launched a drive to boycott the gas-producing state, which they accuse of supporting terrorism and allying with Iran.

Qatar denies the charges and has refused to accept a list of demands issued by the quartet to change its policies.

Defense Secretary Jim Mattis discussed the importance of easing tensions in a phone call with Qatari Minister of State for Defense Affairs Khalid al-Attiyah on Thursday.

Qatar hosts the largest US Air Force base in the region. Saudi Arabia has been a close US ally for decades, and US President Donald Trump sealed a $110 billion arms deal with the kingdom during a visit in May.