Explainer-What's behind deteriorating Somalia-Ethiopia relations?

By Sonia Rao

Somalia has announced the expulsion of an Ethiopian diplomat, marking a further souring of relations between the neighbouring countries related to a port deal Addis Ababa has been negotiating with the breakaway region of Somaliland.

Somalia's foreign affairs ministry said on Tuesday that Ali Mohamed Adan, a counselor at the Ethiopian embassy in Mogadishu, had intervened in Somali state affairs and was being given 72 hours to leave the country.

Here are details about the mounting standoff between the two Horn of Africa nations:

WHY IS SOMALIA UPSET WITH ETHIOPIA?

Somalia was infuriated when Ethiopia signed a memorandum of understanding earlier this year to lease a port from the breakaway region of Somaliland in exchange for possible recognition of its independence.

Somalia considers the deal, which has yet to be finalised, an assault on its sovereignty. Since breaking away in 1991, Somaliland has not been recognised as independent by a single nation.

Turkey has mediated two rounds of talks since July between Somalia and Ethiopia over the deal, but no resolution has been reached and a third round that was planned for September was cancelled.

WHO ARE SOMALIA'S ALLIES IN THE DISPUTE?

Somalia has worked hard to mobilise international support for its sovereignty over Somaliland. The row has drawn it closer to Egypt, which has bitterly opposed Ethiopia's construction of a large hydro dam on a tributary of the Nile River for years.

In August, Egypt delivered its first military aid to Somalia in more than four decades after the MOU was signed.

Somalia has also deepened ties with Ethiopia's historic enemy Eritrea, which seceded from Ethiopia in 1993 and fought a bloody border war with its former ruler from 1998-2000.

Earlier this month, Somalia signed a security cooperation deal with Egypt and Eritrea that was seen as aimed at presenting a common front against Ethiopia.

WHAT IS ETHIOPIA'S POSITION?

Ethiopia, a landlocked nation, wants access to the Red Sea to set up a naval base and commercial port. The country currently relies on neighboring Djibouti for most of its maritime trade, which Prime Minister Abiy Ahmed has said is too costly.

While Somalia may hope tactics like aligning with Ethiopia's rivals will persuade Ethiopia to withdraw from the MOU, they could instead spur Addis Ababa to double down on its position, said Matt Bryden, a strategic adviser to the Sahan think tank.

WHY IS THE STANDOFF WORRYING?

The region sits in a strategic maritime location adjacent to some of the world's busiest shipping lanes. Ships plying those routes have faced months of attacks by Yemen's Houthi militia, and any conflict in the Horn of Africa could further cripple commercial shipping in the area.

The Horn of Africa is also grappling with the threat from al Qaeda affiliate al Shabaab.

Somalia has said that if Ethiopia does not renounce the port deal it will expel the up to 10,000 Ethiopian soldiers stationed in Somalia by the end of the year. The Ethiopian troops are there both as part of a peacekeeping mission and, on a bilateral basis, in order to counter al Shabaab.

Doing so could result in a security vacuum that would likely be exploited by Shabaab fighters, said Omar Mahmood, a senior analyst with the International Crisis Group.