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By Alexander Cornwell

MANAMA, Dec 8 (Reuters) - The United States will maintain its presence in eastern Syria and will take measures necessary to prevent a resurgence of Islamic State, Deputy Assistant Secretary of Defense for the Middle East Daniel Shapiro said on Sunday.

Speaking hours after Syrian rebels announced they had toppled Bashar al-Assad's government, Shapiro called on all parties to protect civilians, particularly minorities, and to respect international norms.

"We are aware that the chaotic and dynamic circumstances on the ground in Syria could give ISIS space to find the ability to become active, to plan external operations, and we're determined to work with those partners to continue to degrade their capabilities," he told the Manama Dialogue security conference in Bahrain's capital.

"(We're determined) to ensure (Islamic State's) enduring defeat, to ensure the secure detention of ISIS fighters and the repatriation of displaced persons," Shapiro added.

Hayat Tahrir al-Sham (HTS), which spearheaded the rebel advances across western Syria, was formerly an al Qaeda affiliate known as the Nusra Front until its leader, Abu Mohammed al-Golani, severed ties with the global jihadist movement in 2016.

Western governments, which have shunned the Assad-led state for years, must decide how to deal with a new administration in which HTS looks set to have influence. HTS is a globally designated terrorist group.

(Reporting by Alexander Cornwell Writing by Nadine Awadalla Editing by Elaine Hardcastle and Frances Kerry)

((Nadine.Awadalla@thomsonreuters.com;))