The US military and intelligence agencies are compiling detailed dossiers on those believed to have attacked the US consulate in Libya ahead of possible retaliation, the New York Times reported.
Citing US officials, the Times reported late Tuesday that the top-secret Joint Special Operations Command (JSOC) was collecting information on the deadly attack last month that killed a US ambassador Christopher Stevens and three other Americans.
US President Barack Obama has vowed to bring those behind the attack to justice, but has faced mounting criticism as officials have struggled to explain how it happened and who was behind it.
The Times said the information now being compiled could be used to launch drone strikes or commando raids against suspects, but that no decision has yet been taken on any potential target.
"They are putting together information on where these individuals live, who their family members and their associates are, and their entire pattern of life," the Times quoted an American official as saying.
The September 11 attack came just weeks before the November 6 presidential election, in which Obama hopes to secure a second term.
The president has touted his foreign policy achievements, especially the killing of Osama bin Laden in May 2011, but has faced accusations of lax security at the consulate in the eastern Libyan city of Benghazi.
The administration has also stumbled in its statements about the attack, initially characterizing it as a violent protest against an anti-Islam Internet video and then calling it a "terrorist" attack linked to Al-Qaeda.
The Times said suspicion has fallen on Ansar al-Shariah, a hardline Islamist militia in Benghazi that may have links to Al-Qaeda.
The United States could face tough choices as it pursues suspects in Libya, where a NATO air operation helped rebels overthrow and kill longtime dictator Muammar Gaddafi last year.
Pro-American sentiment runs high in Libya -- where newly elected leaders condemned the consulate attack -- but could quickly sour if the United States takes military action inside the country.