(CNN) -- U.S. troops lent "limited technical support" in France's bloody and unsuccessful bid in Somalia to rescue an intelligence agent who'd been held hostage for years, President Barack Obama said Sunday.
Obama detailed the U.S. military involvement in the Friday night mission in a letter sent to the leaders of the nation's two legislative chambers. The letter was released publicly as well.
While U.S. forces "provided limited technical support," they "took no direct part in the assault on the compound where it was believed the French citizen was being held hostage," the president explained.
In addition, U.S. military aircraft were available but were not used.
"United States combat aircraft briefly entered Somali airspace to support the rescue operation, if needed," the president wrote. "These aircraft did not employ weapons during the operation."
Obama said he directed the U.S. troops' involvement in the operation "in furtherance of U.S. national security interests, and pursuant to my constitutional authority to conduct U.S. foreign relations and as commander in chief and chief executive."
By 8 p.m., all U.S. forces were out of Somalia.
The moves came after French forces engaged in a fierce gunbattle with militants in their attempt to rescue hostage Denis Allex, who was a member of the DGSE, France's equivalent of the CIA and a part of its defense ministry.
The skirmish in Bulo Marer, about 75 miles northwest of the capital Mogadishu, ended with a French soldier and 17 Islamist fighters dead, according to the French Defense Ministry. Another French soldier is missing.
French Defense Minister Jean-Yves Le Drian told reporters in Paris on Saturday that "everything leads us to believe that Denis Allex was gunned down by his captors." French President Francois Hollande, meanwhile, lamented the "sacrifice" of the two French soldiers and "maybe the assassination" of the hostage.
But the al-Shabaab militia, which is affiliated with al Qaeda, claimed Allex is unharmed and being held in a new location. The group said in a statement that they'll decide the hostage's fate in the next two days.
Allex was abducted on July 14, 2009, while on a mission in Mogadishu in support of the transitional Somali government, the French Defense Ministry said. French media reports suggest that Denis Allex is a pseudonym for the military serviceman.
French officials said they launched the rescue attempt after the terror group failed to negotiate for the hostage's release for years while holding him in inhumane conditions.
The U.S. military has been involved in Somalia before, notably in the ill-fated 1993 Battle of Mogadishu that ended with 18 American soldiers killed.
U.S. forces were in Somalia to try to capture powerful Somali warlord Mohammed Aidid from his stronghold in the war-torn capital and take him to a ship anchored off the nearby coast. But by the end of the 16-hour battle in which commandos tried to seize several of Aidid's top lieutenants, 18 elite Army Rangers and hundreds of Somalis lay dead in the streets of Mogadishu.
The movie inspired the best-selling book "Black Hawk Down" by Mark Bowden and an eponymous, Oscar Award-winning movie directed by Ridley Scott.
Fourteen years later, the U.S. military re-emerged in Somalia by conducting airstrikes targeting al Qaeda-linked operatives in southern Somalia. Other strikes followed, including one in 2008 that killed an al-Shabaab leader and several other senior leaders of his group, according to local officials.
CNN's Greg Botelho and Pierre Meilhan contributed to this report.