Pentagon press secretary Peter Cook told reporters that there is a "small" presence of US military personnel in Libya seeking to establish contact with various militias and other factions to "get a better sense of who the players are" and "who might be worthy of US support."
Cook refused to say if the military personnel included US soldiers.
"We have seen an increase in [Daesh] members, [Daesh]-affiliated groups, if you will, in Libya, and that's a cause for concern," Cook said. "And as a result, we're doing everything we can to monitor that situation and work with our partners, trying to get a better fix on what's happening and, again, consider our options going forward."
In 2011, a US air campaign helped topple Libyan dictator Muammar Gaddafi, creating a power vacuum that has persisted for more than four years.
Defense Secretary Ashton Carter on Thursday said that while the United States does not want Daesh extremists to "sink roots" in Libya, the Pentagon has not yet made a decision about whether to deploy military forces there.
"You see the same kind of ambitions on their part that you see realized in full flower in Syria and Iraq," Carter said. "We don't want to be on a glideslope to a situation like Syria and Iraq. That's the reason we're watching it that closely. That's the reason why we develop options for what we might do in the future."
Last week, Joint Chiefs of Staff chairman General Joe Dunford said that Washington is planning to attack Daesh in Libya. He said the lack of allies on the ground has raised doubts about how the Pentagon would take its strategy in Iraq and Syria and execute it in Libya.
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The United States has already carried out some airstrikes against targets inside Libya, but Dunford insisted he wants the Pentagon to do "more," amounting to "decisive military action" against Daesh, which has a presence on Libya’s central coast.
Washington's plan to train and arm so-called moderate Syrian rebels to fight Daesh was an utter failure and has been an ongoing source of embarrassment for the Obama administration.