Democrats ratchet up campaigning

Both candidates have a furious weekend of campaigning ahead

Democratic presidential hopefuls Hillary Clinton and Barack Obama are on an intense campaign drive in Texas and Ohio before key primaries next Tuesday.

Both states vote in what are seen as must-win polls if Mrs Clinton is to keep her campaign hopes alive.

Mr Obama is now the race's frontrunner, having won 11 consecutive polls.

The Clinton campaign on Friday launched a menacing TV advertisement questioning her rival's credentials, but Mr Obama's team quickly hit back with its own.

Mrs Clinton's ad implied that only she had the experience to make disaster-averting judgements.

The indisputable fact is Barack Obama was right about Iraq when many of us were wrong Senator Jay Rockefeller Clinton's steely resolve Texans' key role in race Last tango in Texas

But Mr Obama's campaign was quick to respond with a retort advertisement suggesting the New York senator's judgement was in question after she voted to authorise the war in Iraq.

In the Republican race, Senator John McCain - who is far ahead of his remaining challengers Mike Huckabee and Ron Paul - hopes to win enough delegates to secure his party's nomination.

Struggling campaign

The two Democratic candidates continued to swipe at each other during speeches on Saturday, with Mr Obama telling supporters that Mrs Clinton's pledge to ignite political change was an empty promise.

"Real change isn't voting for George Bush's war in Iraq and then telling the American people it was actually a vote for more diplomacy when you start running for president," he told a rally in Rhode Island, which along with Vermont is also holding its primary on Tuesday.

I think Hillary will win Ohio but by a very small margin, which may not be enough to save her campaign US voter Faith Barrow-Waheed, Cleveland, Ohio Voters' views: Texas and Ohio

But Mrs Clinton pushed her point at a rally in Texas, highlighting Mr Obama's lack of foreign policy experience.

"We need a president again who is a fighter, a doer and a champion," she said.

The former first lady has been struggling to revive her campaign before Tuesday's critical primaries.

The New York senator has not won a primary or a caucus since the nationwide Super Tuesday contests on 5 February.

She received a further blow on Friday when her rival won the endorsement of Senator Jay Rockefeller, chairman of the Senate Select Committee on Intelligence.

"What matters most in the Oval Office is sound judgement and decisive action," said Mr Rockefeller.

Mr Obama has won the previous 11 primaries and caucuses

"The indisputable fact is Barack Obama was right about Iraq when many of us were wrong."

Correspondents say Mrs Clinton needs to win a majority of delegates in both states to stay in the race to win the Democratic nomination at the party's national convention in August, ahead of the November election.

Mr Obama holds a 6 point lead over Mrs Clinton in Texas and has almost pulled even in Ohio, trailing 42% to 44%, according to a Reuters/C-Span/Houston Chronicle poll released on Friday.