Vice President Joe Biden today delivered the sharpest attack to date on Mitt Romney over foreign policy, accusing the former governor of harboring a "cold war mindset," ignoring the facts of President Obama's record, and waffling on the importance of hunting down Osama bin Laden.

"On this fundamental issue, the contrast between President Obama, his record, and Gov. Romney and his rhetoric cannot be greater," Biden told a crowd of 500 students at New York University.

"If you're looking for a bumper sticker to sum up how President Obama has handled what we inherited, it's pretty simple: Osama bin Laden is dead, and General Motors is alive."

He said later, "You have to ask yourself… if Gov. Romney were president, would he have used the same slogan in reverse?"

Biden, delivering his fifth in a series of campaign issue speeches, painted the presumptive GOP nominee as advocating a return to the "out of touch" policies of President George W. Bush, under whose leadership the U.S. preemptively began a war in Iraq and relied less on multilateral alliances.

"Gov. Romney, I think, is counting on collective amnesia of the American people," Biden said. "Americans know that we cannot afford to go back to the future."

Biden hailed the administration's approach to foreign policy, which he said involved nurturing ties to international groups, ending the war in Iraq, targeting al Qaeda leadership, imposing new sanctions on Iran and signing a new START treaty with Russia , helping Libyan rebels oust Gaddhafi , among other achievements.

He also raised questions about Romney's fitness to be commander in chief, citing the presumptive nominee's 2008 comment that "a president is not a foreign policy expert."

Romney wrongly believes that he can "subcontract" the expertise to other agencies or departments, he said.  "I've been around for eight presidents…That's not how it works."

(Biden said Obama, who took office with little foreign policy experience , has made tough decisions on his own, "with strength and steadiness.")

Turning to Republican's criticism of Obama's record, Biden called it unspecific and out of the mainstream - often ignorant of the facts on the ground.

"We know that even when he agrees with the President of the United States, as he has done, he then goes on to mischaracterize our record to create what is a non-existent contrast," he said. "And most importantly we know that to the extent he's shown any foreign policy vision it's through the glass of a rear view mirror."

On Iraq, Biden charged Romney with flip-flopping, shifting his position on the troop withdrawal - first applauding it, then calling it an enormous error and later saying he would have left tens of thousands of troops behind.

He also attacked Romney's statement in a recent CNN interview that Russia is the United States'  "number one geopolitical foe."

"As my brother would say, go figure," Biden joked. "Sometimes, I don't know if it's a slip of the tongue or a mindset he calls the Russians, Soviets."

On Iran, the vice president called Romney's tweaks of administration policy "apparently ignorant" of the fact that many of his suggestions - such as the need for crippling sanctions and placement of Navy carrier groups in the region - are "exactly what our policy is."

If he wants to launch a war with Iran, Biden said, "he should tell the American people… otherwise it's just talk."

But it is the hunt for Osama bin Laden, the vice president said, that provides the most illuminating contrast between President Obama and Gov. Romney.

"In 2008, while campaigning, Gov. Romney was asked what he would do about Bin Laden. Let me tell you exactly what he said, he said, 'there would be a very insignificant increase in safety' if bin laden was brought to justice. Then he went on to say, 'it's not worth moving heaven and earth, spending millions of dollars, just to catch one person,'" said Biden.

"Here's how candidate Obama answered that question: he said, 'If I have Bin Laden in my sights, I will take him out. I will kill bin laden. I will crush al Qaeda. This has to be our biggest national security priority.'"

"President Obama always means what he says: he said it as a candidate and he kept that promise," he said.

Ahead of the speech, a team of Romney foreign policy advisers accused Biden of presenting a "fantasy narrative" on the administration's record and how Romney would act differently.

"If anything, it is President Obama's track record that has sent a message to our friends and allies, be they in governments or dissident movements, who want to stand with us, lock arms with us, who are looking to American leadership, really left exposed and isolated in a way that I have not seen in American foreign policy history for years," said Romney adviser and former Bush administration official Dan Senor.

"The foreign policy doctrine of all modern presidencies has been peace through strength," said Romney foreign policy adviser Alex Wong. "The only two exceptions to that tradition have been Jimmy Carter and Barack Obama. So if Joe Biden and Barack Obama want to compare a weak Carter-Obama doctrine to peace through strength we're happy to make that comparison."