A soldier missing after a Black Hawk helicopter crashed off the coast of Yemen on Aug. 25 has been declared dead, the U.S. military said late Friday.

Army Staff. Sgt. Emil Rivera-Lopez was a member of the elite 160th Special Operations Aviation Regiment, known as the “Night Stalkers,” when the helicopter went down, official said.

The Pentagon said Rivera-Lopez, 31, was killed during a “training incident,” off Yemen where the US has been supporting Yemeni and Emirati forces battling al Qaeda in the Arabian Peninsula as well as a Saudi-led coalition against Iranian-backed Hauthi militants.

A statement issued by U.S. Central Command said five other service members who were aboard the craft were rescued.

The U.S. military has conducted over 80 air strikes in Yemen since late February. Dozens of US special operations forces have supported ground operations in recent weeks.

Earlier in August, Yemen’s U.S. ambassador said the country did not need a U.S. military presence, but still required U.S. diplomatic help.

“We need the U.S. government to continue to lend its political and logistical support to the legitimate government and the Arab coalition,” Ahmed Awad bin Mubarak told Fox News in an exclusive interview. “This will, in turn, help reinstating the government institutions, which will curb AQAP operations and lead to its demise."

The brutal Yemeni war between the Houthi rebels and Saudi-led coalition is about to enter its fourth year.

At least 25 U.S. service members have been killed in aircraft crashes since July.

Fox News’ Hollie McKay and Lucas Tomlinson and the Associated Press contributed to this report.