An out of control Pakistan is far more dangerous to the United States than Iran seeking 2.6 kg of enriched uranium, Democratic presidential hopeful Senator Joseph Biden has said.

Senator Joseph Biden argued that an out of control Pakistan with nuclear weapons is far more dangerous to the United States than Iran seeking 2.6 kg of enriched uranium.

"This is complicated stuff. The fact of the matter is that the Iranians may get 2.6 kg of highly-enriched uranium. But the Pakistanis have hundreds -- thousands of kilograms of highly-enriched uranium," Biden argued in a debate among Democrats seeking the party's nomination in Philadelphia.

"I will do all in my power to stop Iran from getting a nuclear weapon, but I will never take my eye off the ball. What is the greatest threat to the United States of America: 2.6 kg of highly enriched uranium in Tehran or an out-of-control Pakistan? It's not close," the chairman of the Senate Foreign Relations Committee said.

In what has been billed as the most-lively debate among the Democrats, Biden argued, "If by attacking Iran to stop them from getting 2.6 kilograms of highly-enriched uranium, the government in Pakistan falls, who has missiles already deployed with nuclear weapons on them that can reach Israel, India, then that's a bad bargain."

Front runner Senator Hillary Rodham Clinton came under sharp criticism for her recent vote in the Senate for a resolution calling for the designation of Iran's Islamic Revolutionary Guard Corps as a Foreign Terrorist Organisation.

The Senate passed the motion by 76 to 22 with many Democrats, including Biden voting against it.

Attacking Clinton for her recent vote on the Iran resolution in the Senate, Biden said, "All this talk of war, all this talk of declaring people to be terrorists drives up the price of oil."

"Secondly, we have emboldened Bush, at a minimum, his talk of world war III -- totally irresponsible talk. We have emboldened him to be able to move, if he chooses to move," the top Senator argued.

"Thirdly, this has incredible consequences for Afghanistan and Pakistan. We have driven underground every moderate in Pakistan and in Afghanistan. This literally puts Karzai, as well as Musharraf in jeopardy. The notion is it plays into this whole urban legend that America is on a crusade against Islam," the Delaware Democrat said.

The sharpest rebuke of Clinton came from the 2004 Democratic Vice Presidential nominee John Edwards.

"Senator Clinton says that she believes she can be the candidate for change, but she defends a broken system that is corrupt in Washington," Edwards said, adding, "I think it is crucial for Democratic voters and caucus-goers to determine who they can trust, who's honest, who is sincere, who has integrity."

"She (Clinton) says she'll stand up to George Bush [Images] on Iran. And, in fact, she voted to give George Bush the first step in moving militarily on Iran -- and he's taken it," Edwards argued in the crucial debate in Philadelphia.