NEW ORLEANS, USA (AP) — Isaac was on the verge of becoming a full-blown hurricane today as it rolled over the Gulf of Mexico toward Louisiana, where residents of the low-lying coast left boarded-up homes for inland shelter while people in New Orleans waited behind levees fortified after Katrina.

Forecasters predicted the tropical storm would power up to hurricane strength, which starts at winds of 74 mph (119 kph), later in the day and be at least a Category 1 hurricane by the time it's expected to reach the swampy coast of southeast Louisiana early Wednesday.

The focus has been on New Orleans as the massive and slow-moving storm takes dead aim at the city, but the impact will be felt well beyond the city limits. The storm's winds could be felt more than 200 miles (320 kilometers) from the storm's center.

Early today, Isaac was a large and potent tropical storm packing top sustained winds of 70 mph (113 kph). The storm system was centered about 125 miles (200 kilometers) southeast of the mouth of the Mississippi River at 5 am EDT (1000 GMT) and moving northwest at 12 mph (19 kph), according to the National Hurricane Centre in Miami.

Although Isaac's approach on the eve of the Katrina anniversary invited obvious comparisons, the storm is nowhere near as powerful as Katrina was when it struck on Aug. 29, 2005. Katrina at one point reached Category 5 status with winds of more than 157 mph (252 kph), and made landfall as a Category 3 storm.