Thousands of people have been evacuated from New Orleans as Hurricane Isaac makes its slow approach.
Hurricane Isaac will hit the Louisiana city exactly seven years after it was devastated by Hurricane Katrina, but it is a much less powerful storm.
New Orleans has closed its new floodgates in a bid to protect it from the effects of high waters brought by sustained winds of up to 80 mph (130 km/h).
Isaac killed at least 24 people in Haiti and the Dominican Republic.
It has also caused significant flooding and damage across the Caribbean and forced a day’s delay to the start of the Republican party’s congress in Tampa, Florida.
Hurricane Isaac will hit Louisiana exactly seven years after it was devastated by Hurricane Katrina, but it is a much less powerful storm
At 02:00 local time the Category One hurricane was almost stationery about 70 miles (110 km) south of New Orleans, according to the US National Hurricane Centre (NHC).
Tens of thousands of people have been told to leave their homes in low-lying areas of Louisiana and Mississippi, though a mass evacuation has not been ordered. Storm warnings are also in place in parts of Florida, Texas and Alabama.
Officials say Isaac is likely to weaken before it reaches New Orleans.
“We don’t expect a Katrina-like event, but remember there are things about a Category One storm that can kill you,” said New Orleans Mayor Mitch Landrieu.
Of particular concern are storm surges, with peaks of up to 3.7 m (12ft) forecast in parts of Mississippi and southeastern Louisiana. Rainfalls of up to 50 cm (20 inches) are forecast across wide areas, along with a high chance of isolated tornadoes along the coast.
The bowl-shaped city of New Orleans is particularly vulnerable to storms, with the centre of the city the furthest below sea-level.
But Mitch Landrieu said that the 8m-high levee gate which now protects the areas of the city that were badly flooded in 2005 had been closed since Tuesday morning.
Many residents of New Orleans have chosen to secure their homes but stay put, saying they were not too concerned by Isaac.
“I feel safe,” said Pamela Young from her home in the Lower Ninth Ward, a neighborhood devastated by Katrina.
“Everybody’s talking <<going, going>>, but the thing is, when you go, there’s no telling what will happen. The storm isn’t going to just hit here.”
“If the wind isn’t too rough, I can stay right here. If the water comes up, I can go upstairs.”
Nazareth Joseph, who works at a hotel in French Quarter and was in the city during Katrina, said he had a busy week ahead so would stay where he was.
“We made it through Katrina; we can definitely make it through this. It’s going to take a lot more to run me. I know how to survive,” he told the Associated Press news agency.
By Tuesday night, more than 58,000 homes in New Orleans were reported to have lost power. Outages have also been reported across Louisiana and Mississippi, affecting more than 200,000 homes and business.
President Barack Obama has declared an emergency in Louisiana and Mississippi, allowing federal funds to be released to local authorities.
Speaking from the White House, he warned residents along the Gulf Coast to heed warnings, including those to evacuate, saying: “Now is not the time to dismiss official warnings. You need to take this seriously.”
Shortly before Isaac reached hurricane status on Tuesday, Louisiana Governor Bobby Jindal said the emergency declaration fell short of the federal help he had asked for.
High winds and driving rain are lashing the coast of Haiti as Tropical Storm Isaac moves closer to the shore.
The centre of the storm was last reported as being about 100 km from the Haitian capital, Port-au-Prince.
Aid groups warn that some 400,000 Haitians still living in makeshift camps after the deadly earthquake of 2010 are extremely vulnerable.
Forecasters say Isaac could cause life-threatening flash floods and mudslides in Haiti and the Dominican Republic.
The United States National Hurricane Centre (NHCi) predicts that the storm will move near or over Cuba later on Saturday and approach the Florida Keys on Sunday.
High winds and driving rain are lashing the coast of Haiti as Tropical Storm Isaac moves closer to the shore
The storm could pose a potential threat to Florida during the US Republican National Convention.
Tropical Storm Isaac is no longer expected to become a hurricane as it hits the island of Hispaniola – the island shared by Haiti and the Dominican Republic – but the near-hurricane strength winds and rain have the potential to cause great destruction, especially in Haiti.
“These rains could cause life-threatening flash floods and mudslides,” the NHC warned.
In Haiti, people living in the makeshift squatter camps were “amongst the more vulnerable, should the storm hit the city”, humanitarian group World Vision said.
“Without a stable sanitation system or permanent housing, heavy rain and wind can create much larger problems like disease from water contamination,” the group’s Haiti director Jean-Claude Mukadi was quoted as saying by the AFP news agency.
The country’s president, Michael Martelly, has toured some of the camp sites.
“It looks like the south coast is going to get hit, but again we’re so fragile here in Port-au-Prince that just some rain can cause a lot of damage,” Associated Press quoted him as saying afterwards.
Isaac is also expected to bring rain and wind to nearby Puerto Rico.
Several Cuban provinces are now on a state of alert, as are parts of the Bahamas and the Turks and Caicos islands.