The Yemeni island of Socotra continues to be a source of tension between Saudi Arabia and its biggest partner in the Yemen war, the United Arab Emirates (UAE), according to local sources.

There is "a hidden rivalry and a heated race between the two Gulf states over the island, to dominate the humanitarian and relief fields," a Yemeni source told the Middle East Eye.

"Despite the calmness that surrounds the relationship between Riyadh and Abu Dhabi, both states are struggling to gain the upper hand in humanitarian projects inside Socotra," the source said. "The UAE is jealous of the projects implemented by the Saudis on the island, off the southern Yemeni coast."

In May 2018, the UAE, a pillar of the Saudi-led coalition, faced anger for deploying troops to the Yemeni island of Socotra in the Arabian Sea. In defiance of the UAE's move on the island, Saudi Arabia deployed troops to Yemen's Socotra as a confidence-building measure over complaints by Yemen's government that the UAE deployed troops there without its permission, revealing growing rivalry between the two allies.

The Saudi deployment came after the UAE sent some 300 soldiers, along with tanks and artillery, to Socotra, in a move that drew the ire of Yemenis. In order to ease tension, an agreement was signed with the UAE and Saudi Arabia, according to the Yemeni state news agency Saba. Under the deal, the two countries' troops will withdraw from Socotra and Yemeni forces will be stationed at the island's airport and port, the agency reported.

In Yemen's civil war, the UAE is part of the Saudi-led coalition battling Iranian-backed rebels known as Houthis, who have taken over most of northern Yemen. The UAE entered Yemen's war in March 2015 alongside Saudi Arabia to back Yemen's internationally recognized government, which the Houthis had pushed out of the capital, Sanaa. The UAE has largely handled ground operations in the conflict while the Saudis have carried out airstrikes.