The Fiji Weather Office says tropical cyclone Tomas could pose a major threat to Fiji by late Sunday.
It has just named the cyclone which formed from a tropical depression north of Wallis.
A senior forecaster, Matt Boterhoven, says it has intensified over the past 12 hours as it heads in a west south-west direction.
He says it's likely to eventually move in a southerly direction and warnings are out for Wallis and Futuna.
People there have been told to expect damaging gale force winds and flooding.
Mr Boterhoven says Fiji also lies in its path and could be affected by late Sunday.
He says by that stage the system is likely to have intensified further.
"Given the environmental conditions -it's got nice warm water to provide a bit of fuel for the cyclone. Good convection, not too much shear, so it looks like we could see the system develop into a category 3 and maybe even a category 4 system as it approaches Fiji."
Meanwhile, a tropical low over northern Vanuatu is also expected to become a cyclone as it moves to the northwest.
The northern provinces of Torba and Sanma are expecting damaging gale force winds from later today.