WASHINGTON (Reuters) - The U.S. secretaries of state and defense on Tuesday called on all sides in the dispute between Qatar, Saudi Arabia and the United Arab Emirates to work to calm tensions, saying a united Gulf Cooperation Council bolstered regional stability.

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“It is critical that all parties minimize rhetoric, exercise restraint to avoid further escalation and work toward a resolution,” Secretary of State Rex Tillerson said at a joint appearance of the U.S. and Qatari foreign and defense ministers.

The UAE, along with Saudi Arabia, Bahrain and Egypt, cut off travel and trade ties with Qatar last June, accusing it of supporting terrorism and their arch-rival Iran. Doha denies the charges and says the countries aim to curtail its sovereignty.

Qatar’s Foreign Minister Sheikh Mohammed bin Abdulrahman al-Thani said that the meeting - the first in what is planned as an annual U.S.-Qatar Strategic Dialogue - was taking place “despite the difficult circumstances” in which “Qatar and its people have been illegally and unjustifiably blockaded.”

He expressed gratitude to the U.S. Congress and the Trump administration for taking what he said was a “just position” on the trade and travel boycott.

President Donald Trump’s stance on the crisis has been complicated. He initially tweeted what appeared to be support for the boycott, but in September offered to mediate. In a call earlier this month, he thanked Qatar’s Emir Sheikh Tamim bin Hamad al-Thani for his efforts to counter terrorism.

U.S. Defense Secretary James Mattis said on Tuesday it was critical for the GCC to regain the cohesion among its members, all of whom are U.S. partners: Bahrain, Oman, Kuwait, Qatar, Saudi Arabia and the UAE.

“A united Gulf Cooperation Council bolsters our effectiveness on many fronts, particularly on counterterrorism, defeating ISIS Daesh, and countering the spread of Iran’s malign influence,” Mattis said, referring to the Islamic State militant group.

Qatar is host to U.S. and international forces at Al Udeid Air Base, which is home to the Combined Air Operations Center. The center coordinates an array of data and intelligence from satellites, drones, radar and U.S. planes flying over hot spots in the Middle East and bombing Islamic State positions.

The U.S. and Qatari officials signed three memorandums of understanding on security cooperation and other issues. Tillerson and al-Thani also welcomed progress toward resolving a dispute over civil aviation.

State-owned Qatar Airways has agreed to release detailed financial statements, the U.S. government said on Tuesday, as part of a response to accusations by U.S. airlines that the carrier had been illegally subsidized by its government.