Mexico City/Washington  - Hurricane Bill, the first major Atlantic storm of the season, was downgraded to a category two Friday and was expected to spare the United States and Bermuda its worst effects, the US Hurricane Centre said.

A tropical storm warning was still in effect for Bermuda, but the Miami-based centre stepped back from an earlier prediction of "significant costal flooding" on the island.

Bill was maintaining winds as high as 175 kilometres per hour, making it a category two storm on the five-point Saffir-Simpson scale.

But the "core" of the hurricane would likely pass west of Bermuda and turn north along the eastern coast of the United States and Canada, where it was expected to weaken over the weekend.

The storm was located 465 kilometres south-southwest of Bermuda by Friday afternoon. Bill had become "a little less organized" over night, the centre said.

Bill was still predicted to bring strong rains and high waves to Bermuda and the East Coast of the United States. The first hurricane of the season had strengthened into a category four on Thursday.

Last year, several tropical storms caused heavy damage in the Caribbean, in particular on Cuba and Haiti. Both countries have yet to fully recover.  (dpa)