MIAMI – A hurricane warning was issued Sunday for Puerto Rico and the northern coast of the Dominican Republic as Tropical Storm Irene dumped heavy rain in the Caribbean.

The storm could hit southern Florida by the end of the week.

Forecasters at the U.S. National Hurricane Center in Miami said Irene could become a hurricane by today. On Sunday, the storm had maximum sustained winds of 50 mph and was moving west-northwest at 20 mph. Sustained winds must reach 74 mph for the storm to become a hurricane.

The warning in the Dominican Republic stretches from its border with Haiti in the south to Cabo Frances Viejo on the north coast.

Meanwhile, a hurricane watch has been issued for the U.S. Virgin Islands. A tropical storm warning is in effect for Haiti, the U.S. Virgin Islands and other islands.

Irene was 235 mile east-southeast of Ponce, Puerto Rico. It was expected to pass near Puerto Rico sometime late Sunday or early today.