U.S. Republican presidential candidate John McCain quickly lashed out after his Democratic rival, Barack Obama, revealed his choice for vice president.
The McCain campaign released a statement and launched a television ad Saturday - hours after Obama announced that he had selected Delaware Senator Joe Biden.
The television ad uses a 2007 clip in which Biden says he does not believe Obama is ready to be president.
In McCain's campaign statement , spokesman Ben Porritt says there has been no harsher critic of what he called Obama's lack of experience than Joe Biden.
McCain may announce his running mate during a rally on August 29, three days before the start of the Republican National Convention.
His top contenders are said to include former Massachusetts Governor Mitt Romney, Minnesota Governor Tim Pawlenty, and former Pennsylvania Governor Tom Ridge, who was also the country's first Homeland Security director.
Some information for this report provided by AP and Reuters.