Tropical storm Rene is expected to become a hurricane later this week and then weaken over the open waters of the Atlantic Ocean, the US National Hurricane Center (NHC) said.
"Additional strengthening is forecast during the next 48 hours," Xinhua news agency quoted the NHC as saying on Wednesday.
"Some weakening is forecast during the next couple of days."
The storm is forecast to continue moving northwest through Friday night and Saturday.
It is however, not expected to have a direct impact on the US, said a Fox News report.
September produces the most Atlantic Ocean basin tropical activity historically, said the report.