A new hurricane has formed over the Pacific off Mexico, prompting local officials to issue a tropical storm watch for parts of Baja California state, US forecasters said Monday.

The hurricane, named Paul, packed maximum sustained winds of nearly 75 miles (120 kilometers) an hour, with stronger gusts, the Miami-based National Hurricane Center said.

But the storm was expected to start weakening by Tuesday when it is expected to be near the west coast of the Baja peninsula, the centre noted.

No landfall is currently forecast.