"I think New Orleans can be confident in its hurricane protection system because it is better and it is stronger," Johnson said after a helicopter tour.

"We've spiraled in new information as we've learned some things, working with the technical experts to tell us what it is we need to do to build this system using the best materials, science, engineering and construction practices."

But it is not certain it will protect against all storms, officials said. Katrina came ashore as a Category 3 hurricane.

"There will always be a risk," said Maj. Gen. Don Riley, the Corps' director of civil works. "Another Katrina, on a different track, at a different speed, moving slower with more rainfall could do damage."

A series of levee breaches during the Aug. 29 storm flooded 80 percent of New Orleans and left parishes like St. Bernard and lower Plaquemines with virtually no structure undamaged.

These areas still bear the scars, including gutted homes and residents living in government-supplied trailers as well as many damaged businesses that have yet to reopen.

BIG IMPROVEMENTS

Residents and some independent engineers sharply criticized the Corps for faulty design and poor maintenance of levees.

In its first phase of improvements, the Corps spent more than US$800 million to repair levees to pre-Katrina strength or better. Billions of dollars of major improvements are also planned over the next six years, although Washington has yet to approve all the money.

"I've always been critical of the Corps, but I have to tell you the Corps has done an excellent job," said St. Bernard Parish President Henry "Junior" Rodriguez.

"I would only hope that one thing doesn't happen -- that you don't restore this levee to the pre-Katrina condition because it's the best levee that's ever been in St. Bernard Parish"

The parish borders New Orleans to the East. Katrina's storm surge swamped towns like Chalmette and Meraux and killed 130 people. The hurricane killed 1,500 in Louisiana.

New Orleans-area residents were rattled this week by reports that a 400 foot (122 metre) stretch of levee near the town of Buras in southern Louisiana slumped. The Corps said the problem was one of weight and insufficient support at ground level, and that it had been fixed.

Temporary floodgates and pumps at mouths of two canals on the north side of New Orleans are also behind schedule, but officials said short-term fixes are in place if needed.

The state of the levees is an overriding worry as the 2006 hurricane season begins and the ravaged New Orleans region struggles to recover.

"One of the big concerns is that there could be a storm that surpasses Katrina in strength," said Sue Sturgis, author of a hurricane preparedness report by non-profit group Gulf Coast Reconstruction Watch.