MINNESOTA - REPUBLICAN vice-presidential nominee Sarah Palin revealed on Monday her unmarried teenaged daughter is pregnant, in the latest bombshell to rock the party's Hurricane Gustav-curtailed convention.

Mrs Palin said her daughter Bristol, 17, would have the baby and marry its father, as the convention held a shortened first day, shorn of political rhetoric out of respect for those sheltering from Gustav's wrath.

The curtailed convention will cost presumptive nominee John McCain some of his precious opportunity to take his unfiltered case to US voters, a week after his Democratic rival Barack Obama's spectacular jamboree in Denver.

A new CBS/New York Times poll on Monday suggested that Mr McCain needed a boost, putting Mr Obama and his vice presidential pick Mr Joseph Biden up 48 per cent to 40 per cent, ahead of the November 4 election.

Mr McCain's surprise choice of Mrs Palin as his running mate last week electrified the Republican Party's social conservative base, in particular evangelical Christians who had been reluctant to back Mr McCain.

And early signs suggested that powerbase was still intact for Mrs Palin, a 44-year-old abortion foe, despite the revelations about her daughter.

'Our beautiful daughter Bristol came to us with news that as parents we knew would make her grow up faster than we had ever planned,' she said in a statement with her husband Todd.

'We're proud of Bristol's decision to have her baby and even prouder to become grandparents. As Bristol faces the responsibilities of adulthood, she knows she has our unconditional love and support,' they said.

'Bristol and the young man she will marry are going to realise very quickly the difficulties of raising a child, which is why they will have the love and support of our entire family.'

Mrs Palin, who Democrats have savaged as too inexperienced in foreign policy to serve a 'heartbeat' away from the Presidency, was in the convention city of St Paul on Monday with no public engagements scheduled.

Mr McCain earlier flew into Philadelphia, as he monitored the fallout from Hurricane Gustav, which was hammering the Louisiana coast and prompted the Republican candidate to severely curtail the convention's opening day.

Mrs Palin's announcement about her daughter appeared to be a bid to hit back at unsourced rumours on liberal blogs that her daughter was the mother of the Alaska governor's 5th child, Trig.

A McCain campaign official said on condition of anonymity that the Arizona senator knew about the condition of Mrs Palin's daughter, who is reportedly 5 months into the pregnancy, when he asked her to be his vice-presidential nominee last week.

As thousands of protestors rallied outside to demand an end to the Iraq War, the convention delegates met in a shortened session overshadowed by Gustav and memories of Hurricane Katrina.

First Lady Laura Bush and Mr McCain's wife Cindy gave speeches to kickstart a emergency fundraising drive as the political jamboree turned into a Gustav relief rally.

The party scurried to change its convention plans amid fears of being seen to stage a political celebration while a monster storm pummels the Louisiana coast.

Democratic nominee Barack Obama meanwhile appealed to his two million donors for financial aid for Hurricane Gustav victims on Monday, as he made plans to return to Chicago to assess the aftermath of the storm.

Mr Obama also got a federal briefing about the hurricane's destructive charge ashore near New Orleans, after Mr McCain ordered a halt to all political activities at his party's nominating convention.

'Today, the thoughts and prayers of all Americans are with those in the path of Hurricane Gustav - and many of you are asking what you can do to help,' Mr Obama said in an email to his supporters.

Mr Obama was later returning home to Chicago to monitor the storm.

Mr McCain aides have yet to decide if the four-day convention can resume its normal programme on Tuesday.

They also signalled Mr McCain would likely deliver his acceptance speech, due on Thursday, at the convention, and not as had been previously suggested from the hurricane disaster zone. -- AFP