The communique was issued at the end of the talks that gathered US Secretary of State John Kerry and top officials from more than 20 other nations to discuss ways to strengthen Libya's fledgling Government.
The move reflects worries over a widening presence of Isis (Islamic State) militants in Libya, which has been divided between rival administrations and plagued by increased lawlessness.
In February, US President Barack Obama urged greater efforts to keep Isis from "digging in" across Libya.
A major complication in Libya is identifying which groups will align themselves with the unity Government.
US Special Operations troops have been stationed at two outposts in eastern and western Libya since late 2015, tasked with lining up local partners in advance of a possible offensive against Isis, US officials said last week.
A US air attack in February targeted a suspected Isis camp, killing at least 40 people including a senior operative, Noureddine Chouchane, who was linked to attacks against Western tourists in neighbouring Tunisia.
- Washington Post, AP