Assem Qanso's request comes days after the ambassador, Maura Connelly, had emphasized the need for the Lebanese army to protect members of the Syrian opposition and refugees living in Lebanon, The Daily Star in Beirut reported.
Qanso, the former head of the Baath party in Lebanon, called for Connelly's expulsion after meeting with Mikati and a delegation of deputies from Baalbek.
In a statement issued Tuesday after Connelly met with Lebanese Defense Minister Fayez Ghosn, the U.S. Embassy said, "Ambassador Connelly emphasized the importance the United States places on the Lebanese armed forces' role in protecting members of the Syrian opposition residing in Lebanon, as one of Lebanon's international legal obligations that also include support and funding of the Special Tribunal for Lebanon."
Under President Bashar Assad Syria has violently cracked down on protesters in the past seven months, killing nearly 3,000 people.
Lebanon has maintained a neutral policy on the protests in Syria and abstained from a recent vote on a U.N. Security Council resolution condemning Syria and hinted it could face sanctions if it continues its crackdown on protesters.
The resolution was vetoed by China and Russia.