The Pentagon on Wednesday said it was still investigating whether U.S. strikes in Syriaon Tuesday killed a leader of the al Qaeda-linked Khorasan group, adding that it could take time to determine.

"We just don't have a confirmation to make at this point," said Pentagon spokesman Colonel Steve Warren. "We don't have personnel on the ground to verify, so we're continuing to assess."

Reuters quoted a U.S. official earlier on Wednesday saying the United States believed one of those killed in the strike against the group was Mohsin al-Fadhli, who the U.S. government has identified as a al Qaeda financier close to al Qaeda founder Osama bin Laden.