The United Nations has enforced the embargo since the 2011 Libyan revolution that saw the ouster of Moamer Kadhafi's regime.
During a meeting at the Pentagon, Sarraj told Mattis that Libya has made progress against Islamist extremists and the Islamic State group.
"We are also facing another challenge, which is the lack of capabilities and means, and this includes also the embargo on the armament that the National Accord Government is facing," he said.
"We hope that this embargo will be partially ended, at least against some of the military branches such as the presidential guard and the coast guard so that they can complete their mission."
The United Nations in September launched a new plan to bring stability to Libya, which has been in chaos since the ouster of Kadhafi.
Sarraj is due to meet President Donald Trump in Washington today.