Ryad (AFP)

The capture of the Yemeni city of Aden by separatists backed by the United Arab Emirates at the expense of the Saudi-backed government is evidence of flaws in the relationship between Saudi and Emirati allies, experts say.

Ryad and Abu Dhabi have sought to show unity in the crisis, but last week's deadly fighting between their proteges in southern Aden undermines the common front in the Iran-backed Houthi rebels' war .

Saturday's seizure of separatists from the presidential palace in Aden is another blow to Saudi Arabia, which has been carrying out the costly armed intervention in Yemen since 2015, but failed to defeat the Houthis.

This battle of Aden opposed units loyal to President Abd Rabbo Mansour Hadi, supported at arm's length by Ryad, the force called "Cordon security", formed by Abu Dhabi. All are, however, theoretically allied against the Houthis, who control the capital Sanaa, to the north.

Mohammed Ben Zayed, the strongman of Abu Dhabi, whose country is an important member of the coalition intervening in Yemen, traveled to Saudi Arabia, near Mecca, on Monday for talks with Saudi leaders.

The two countries have called on the disputing parties in Aden to "dialogue" and "the reason," according to an Emirati statement. The text also emphasized that Saudi Arabia was "a key pillar of regional security and stability".

But, behind this displayed cohesion, there is above all realpolitik, underline experts.

In its war against the Houthis, "Saudi Arabia needs the fighting force of the south" led by the Emirates, told AFP Fatima Abo Alasrar, a Yemeni analyst based in Washington.

If the Saudis want to win this conflict against the Houthis, "they will have to encourage a ceasefire and reconciliation between the government and the separatists," he added.

- Diverging objectives -

Divisions in southern Yemen are partly the result of diverging goals between Saudis and Emiratis.

The UAE has long regarded the south as a vital base for expanding its influence in the Red Sea and Horn of Africa. They financed and formed various groups that are now favorable to them.

Their big Saudi neighbor considers the Houthis as an existential threat on its southern border, comparing these Yemeni rebels to Lebanese Hezbollah.

Yemen has become, over the years, the proxy battleground between Ryad and Tehran, while the Houthis have stepped up their drone and missile attacks on Saudi cities.

In this context, the announcement in July by the Emirates of a reduction of their troops in Yemen was a first setback for Ryad, despite assurances from Abu Dhabi that it was not a complete withdrawal.

"It's a hard blow ... It will be difficult for Ryad to replace the UAE," said Olivier Guitta, managing director of GlobalStrat, a geopolitical risk consulting firm.

- Hijacking weapons? -

Now, more than ever, Ryad needs UAE support to bring separatists from southern Yemen to the negotiating table.

The Saudi Foreign Ministry said it had invited disputing parties in Aden to talks in the kingdom. But no date has been announced.

Saudi Deputy Defense Minister, Prince Khaled bin Salman, warned that internal struggles could be exploited not only by the Houthis, but also by other groups active in Yemen such as al-Qaeda and the Islamic State group ( EI).

The violence in Aden has increased the risk of Western weapons falling into the hands of local militias, especially after the US Senate failed last month to prevent the controversial sale of $ 8.1 billion. armament at Ryad.

"End-use monitoring has raised concerns over the transfer of US arms by Saudi Arabia and the Emirates to various factions in Yemen, especially the southern separatists," said Becca Wasser, an analyst at RAND Corporation. based in the United States.

The Gulf states reject such claims, but Aden's precipitous withdrawal of government forces, armed by Ryad, revives the fear that their equipment will fall into the hands of the separatists.

© 2019 AFP