The U.N.’s highest court for disputes between countries sided with Qatar on Tuesday in its legal fight with several Gulf states that imposed an air blockade against Doha.

Saudi Arabia, the United Arab Emirates, Bahrain and Egypt severed political, trade and transport ties with Qatar in June 2017, accusing Qatar of backing Islamist radicals and Iran. Doha denies the charges and says the embargo aims to undermine its sovereignty.

Washington has strong ties with all the states involved, including Qatar, which hosts the largest U.S. military base in the region, and sees the rift as a threat to efforts to contain Iran. It has pushed for a united Gulf front.

The International Court of Justice’s 16-judge panel ruled that appeals filed by Qatar’s neighbours against several decisions of the International Civil Aviation Organization (ICAO) should be dismissed. The court also confirmed that it was the ICAO that has jurisdiction in the airspace row.

Qatar objected to the closing of the airspace in a complaint to the ICAO, and that case continues. Qatar has limited airspace and has had to rely on that of Iran.

In a reaction to Tuesday’s ruling, Qatar said it welcomed the decision “that it has the right to challenge airspace restrictions imposed by Saudi Arabia, UAE, Bahrain and Egypt before the U.N.’s aviation body”.

The UAE issued a statement vowing to fight on at the ICAO, saying it “will now put its legal case to ICAO supporting the right to close its airspace to Qatari aircraft”.

Diplomats and Gulf sources have told Reuters that the United States has been trying to convince Saudi Arabia and its allies to reopen their air space to Qatar, but that the mediation efforts since the start of 2020 have so far been unsuccessful.

The UN aviation agency, which is headquartered in Montreal, does not impose binding rules, but wields clout through safety and security standards that are usually followed by its 193-member countries. There is also a dispute resolution mechanism under the 1944 Chicago Convention which is overseen by ICAO.