The sides have only made an oral agreement, the spokeswoman specified.
Earlier in the day, Tanju Bilgic, the country’s Foreign Ministry spokesman, said the Incirlik base agreement had been sealed by Turkey.
"Mr. Bilgic meant achievement of a verbal agreement between Turkey and the United States on the Incirlik base," the ministry’s spokeswoman said.
Washington has long asked Ankara for the use of the Incirlik air base to launch air raids against IS positions in Syria and Iraq. The facility is already used by the US Air Force for logistical and humanitarian purposes.
Previously, Turkey refused to actively participate in anti-ISIL coalition operations.
As the security situation in Turkey has deteriorated in recent weeks, the country responded with a military campaign against ISIL jihadists in Syria. The military operation followed an allegedly IS-organized explosion in the city of Suruc on July 20, which killed 32 people.