On Tuesday morning, Vanuatu Meteorological Service (VMS) said the system was 175km from Vanua Lava, northern Vanuatu.
VMS forecaster Iuma Bani said the system was set to become a category three storm later Tuesday.
It was moving slowly, Bani said.
"We're not expecting the system to be here in Vila tonight, maybe tomorrow, sometime tomorrow morning because it is moving quite slowly," he said.
"Once it starts moving south, then it will start to speed up a little bit."