Republican presidential candidate John McCain has suspended most events planned for day one of his party's convention because of Hurricane Gustav.
The convention, due to begin on Monday in Minneapolis, was scaled down as the fierce storm approached New Orleans.
Gustav, now a Category Three storm, is due to make landfall on Monday.
Residents of New Orleans have been told to leave the city. The mayor has imposed an overnight curfew and warned looters they will be sent to jail.
Speaking in Mississippi, Mr McCain said it was important to tone down the traditional pomp and flair of convention week.
Predicted route of Hurricane Gustav (31 August 2008)
"Of course this is a time when we have to do away with most of our party politics," Mr McCain told reporters.
President George W Bush and VP Dick Cheney have scrapped plans to address the convention on Monday. Mr Bush said he would instead go to Texas to monitor relief efforts.
Mr McCain's campaign chartered a jet to fly worried delegates back to their home states threatened by the hurricane, which is set to hit the Louisiana coast on Monday.
'Hope and pray'
After returning from a tour of relief preparations in Mississippi, he said convention delegates needed to "take off our Republican hats, and put on our American hats and we say America, we're with you".
The BBC's Adam Brookes, in Minnesota for the convention, says the Republicans are keen to avoid the kind of political damage incurred by the Bush administration's clumsy response to Hurricane Katrina three years ago.
Plainly the backdrop of images of destruction reminding Americans of Katrina will be horrible for the Republicans
BBC North America editor Justin Webb
Republicans clearly cannot afford to be seen hosting glamorous political events, while the people of New Orleans are once again fleeing their city, he says.
"I hope and pray we will be able to resume some of our normal operations as quickly as possible," McCain told reporters via a video link from St Louis.
"I have every expectation that we will not see the mistakes of Katrina repeated," he added.
Mr McCain's convention manager Rick Davis said the convention would open for just over two hours on Monday, solely to go through procedures necessary under law to begin the process of nominating a president and vice-president.
The formal business of the convention includes, on Wednesday, the formal nomination of the Arizona senator for president and Alaska Governor Sarah Palin as his running mate.
The streets of New Orleans were empty as a curfew loomed
Mr McCain's acceptance speech, set for prime time on Thursday evening, is deemed to be among the most important events of the campaign for his chances of winning the White House in November.
Meanwhile, Democratic nominee Barack Obama said he would open up his vast donor list to channel money or volunteers to help recovery efforts, in response to Gustav.
"We can activate an e-mail list of a couple [of] million people who want to give back," Mr Obama told reporters after attending church in Lima, Ohio.
New Orleans residents have been fleeing in their thousands after Mayor Ray Nagin ordered a full evacuation of the city.
FLASHBACK TO KATRINA
Katrina struck US Gulf Coast in August 2005 as a category three storm, killing more than 1,800 people
New Orleans was 80% flooded after storm surge breached protective levees
US Government was blamed for slow, botched response that exacerbated disaster
Hundreds of thousands of people were displaced
Roads out of the Louisiana port - much of which lies below sea level and is protected from flooding only by a fragile system of levees - have been crammed with traffic.
Mr Nagin said that the first storm winds could hit New Orleans as early as daybreak on Monday and the hurricane could reach Category Four strength.
America's homeland security chief, Michael Chertoff, said the main evacuation was going well but he warned that people hoping to ride out the storm would be "exceptionally foolish".
The evacuation comes almost exactly three years after Hurricane Katrina devastated New Orleans.
In 2005, three-quarters of the city was flooded after a storm surge breached its protective levees. More than 1,800 people died in coastal areas.
Gustav has already claimed the lives of more than 80 people in the Caribbean, causing widespread damage in Haiti, the Dominican Republic and Jamaica over the past week. At least 300,000 people were evacuated in Cuba as the storm brought extensive flooding and some severe damage, but no reports of deaths.