Somalia’s civil aviation authority threatened to block Ethiopia Airlines, Africa’s biggest carrier, from flying into the country amid a dispute over the sovereignty of a breakaway region.

The two Horn of Africa nations have been at loggerheads since Somaliland agreed in January to allow landlocked Ethiopia to set up a naval base on its shores in exchange for a stake in the national carrier. The deal will also allow Ethiopia to build a port and a transport corridor in the region, which Somalia considers an integral part of its territory.

The Somali Civil Aviation Authority complained that Ethiopian Airlines had resorted to removing references to destinations in Somalia and was instead using only airport codes to circumvent the sovereignty issue.

“If these issues are not resolved by Aug. 23, the SCAA will have no choice but to suspend all Ethiopian Airlines flights to Somalia,” the agency said in a letter to the carrier.

Ethiopian Airlines flies into Hargeisa, the main city in Somaliland, Garowe in the semi-autonomous Puntland region, and Mogadishu, Somalia’s capital. Other carriers that fly to Somalia include Flydubai, Kenya Airways and Turkish Airlines.

A former British protectorate, Somaliland united with Italian Somalia in 1960 after independence, before breaking away in 1991 after a civil war erupted. The enclave holds regular elections, issues its own passports and currency and is generally more stable and economically developed compared with the rest of the country.