While Ankara has repeatedly stated that its operations in Syria only targeted the Islamic State group and US-backed Kurdish militants, which the Turkish government considers to be terrorists, Damascus stressed that the Turkish Army had never asked permission to act on Syrian territory.
Pence and his wife, Karen, served a traditional Thanksgiving meal of turkey, cranberry sauce and other fixings to some 700 troops at the base, which Trump visited in a similar surprise trip past year. The U.S. and Syrian Kurdish forces refer to it as a "security mechanism".
On October 9, Turkey launched a military incursion into northern Syria, codenaming it Operation Peace Spring.
The incident occurred on Saturday in the town of Tel Abyad, near Syria's border with Turkey.
In neighboring Syria, after declaring the near-complete withdrawal of USA forces from Syria, Trump decided that roughly 800 would stay to keep eastern Syria's oil fields from falling back into the hands of the Islamic State.
Trump also agreed to keep about 150 United States troops at a base in southern Syria as a check on Iranian influence in the region.
Kurdish-led Syrian forces expelled IS from its last patch of land in March, but the militants have continued to claim deadly attacks.
"We spoke about the unrest that's been taking place in recent weeks here in Iraq", Pence told reporters. He said the Trump administration is working to secure another pay increase for the armed services and suggested the ongoing impeachment inquiry in Washington was slowing the way.
Pence's visit to Iraq comes as the country has been plagued by widespread anti-corruption protests. Traveling on a military cargo plane, he landed first at Al Asad Air Base northwest of Baghdad and talked by phone with Abdul Mahdi.
Fifteen people have died and over 100 have been wounded during three days of fierce clashes in central Baghdad, according to officials cited by the Associated Press.
Later Saturday, Mr. Pence and his wife, Karen, served Thanksgiving lunch to about 150 troops, and the vice president delivered remarks to about 200 personnel.
Vice President Mike Pence visited Iraq on Saturday to reassure Iraqi Kurds of US support after President Donald Trump's decision to withdraw troops from northern Syria drew criticism that Washington had betrayed its Kurdish allies there.