WASHINGTON -- The United States helped France last week during an attempted rescue of a secret agent captured by insurgents in Somalia, President Barack Obama confirmed on Sunday in a letter to Congress.

The French team was trying to free Denis Allex, held since 2009 by al-Qaida-linked al-Shabab, but insurgents apparently killed their hostage during the raid, along with a commando.

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The French defense ministry said that 17 Somali fighters also died in the fight.

"United States combat aircraft briefly entered Somali airspace to support the rescue operation, if needed. These aircraft did not employ weapons during the operation," Obama said in his letter to U.S. lawmakers.

Obama sent the letter to Congress to fulfill his obligations under the War Powers Resolution, which requires him to inform policymakers within 48 hours of committing armed forces to military action without congressional authorization.

Obama said the operation was warranted to further U.S. national security interests, and said U.S. forces "took no direct part in the assault on the compound where it was believed the French citizen was being held hostage."

Editing by Philip Barbara, Reuters

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