Stalked by memories of the Hurricane Katrina tragedy, Mr McCain shelved most of the convention's opening day. President George W. Bush and Vice President Dick Cheney cancelled plans to attend to concentrate on the deadly storm.

Party leaders scurried to change their plans amid fears at being seen to stage a political celebration while a killer storm pummels the Louisiana coast.

'The challenges are grave and we have to, as you know, put our country first,' said Senator McCain at a rally in O'Fallon, Missouri, late on Sunday.

'We will put aside our political hats and put on our American hats and we will do everything America needs to do and America must do because the nature of our nation is to help any of us.'

Mr McCain's Democratic rival Senator Barack Obama said he would make his campaign's mammoth donor list available to channel money and volunteers towards relief efforts.

'We can activate an email list of a couple million people who want to give back,' Mr Obama told reporters after attending church in Lima, Ohio.

'I think we can get tons of volunteers to travel down there if it becomes necessary,' said Obama, who was formally installed as the Democratic nominee at a triumphant convention last week.

The Republican convention will open for two-and-a-half hours on Monday simply to put in place the start of the legal process needed to nominate a presidential and vice presidential candidate, officials said.

'We will refrain from any political rhetoric which would be traditional in an opening session,' Mr McCain's campaign manager Rick Davis said.

'Right now we have a horrible storm bearing down on the Gulf, people should be more concerned about that than a political campaign and that is the way we are going to let the chips fall.'

It was unclear whether the four-day convention would resume as planned on Tuesday.

Hurricane Gustav's approach has revived painful memories for Republicans of Katrina, which flooded large sections of New Orleans in 2005 and killed 1,800 people in the region.

Mr Bush took the lion's share of the blame for the botched recovery effort after Katrina, which saw poverty-stricken people abandoned in the city, and the Republican brand has still to recover. -- AFP