Tillerson “will meet with senior Kuwaiti officials to discuss ongoing efforts to resolve the Gulf dispute,” the state department.

:: Underscoring US concerns about the Qatar crisis, Secretary of State Rex Tillerson is set to visit Kuwait, which is mediating in the dispute, on Monday.

Tillerson “will meet with senior Kuwaiti officials to discuss ongoing efforts to resolve the Gulf dispute,” the state department said on Thursday.

The US has become “increasingly concerned that the dispute is at an impasse at this point,” Heather Nauert, the spokesperson for the department, said.

Saudi Arabia, the United Arab Emirates, Egypt, and Bahrain 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.