“South Africa doesn’t have that kind of money,” National Treasury spokesperson Jabulani Sikhakhane said.
Zimbabwean officials were not immediately available for comment.
Zimbabwe was hit by anti-government protests last week after a hike in fuel prices stoked anger over an economic crisis.
Police say three people died during demonstrations that turned violent in the capital Harare and second city Bulawayo. But human rights groups say evidence suggests at least a dozen were killed.
Zimbabwean President Emmerson Mnangagwa said on Sunday that he would return home from a European tour and skip the World Economic Forum in Davos to address the crisis.