(AP) - At odds early and often, Joe Biden and Republican Paul Ryan squabbled over the economy, taxes, Medicare and more Thursday night in a contentious, interruption-filled debate. "That is a bunch of malarkey," the vice president retorted after a particularly tough Ryan attack on the administration's foreign policy.

"I know you're under a lot of duress to make up for lost ground, but I think people would be better served if we don't interrupt each other," Ryan said later to his rival, referring to Democratic pressure on Biden to make up for President Barack Obama's listless performance in last week's debate with Mitt Romney.

There was nothing listless this time as the 69-year-old Biden sat next to the 42-year old Wisconsin congressman on a stage at Centre College in Kentucky.

Ninety minutes after the initial disagreement over foreign policy, the two men clashed sharply over steps to reduce federal deficits.

"The president likes to say he has a plan," Ryan said, but in fact "he gave a speech" and never backed it up with details.

Biden conceded Republicans indeed have a plan, but he said if it were enacted, it would have "eviscerated all the things the middle class care about."

The debate took place a little more than a week after Obama and Romney met in the first of their three debates - an encounter that has fueled a Republican comeback in opinion polls.

With Democrats eager for Biden to show the spark the president lacked, he did so.

Unprompted, he brought up the video in which Romney had said 47 percent of Americans pay no federal income tax, view themselves as victims and do not take responsibility for their own lives.

"It's about time they take responsibility" instead of signing pledges to avoid raising taxes, Biden said - of Romney, Ryan and the Republicans.

The serial disagreements started immediately after the smiles and handshakes of the opening.

Ryan said in the debate's opening moments that U.S. Ambassador Chris Stevens had been denied sufficient security by administration officials. Stevens died in a terrorist attack on the U.S. Consulate in Benghazi on Sept. 11.

"Not a single thing he said is accurate," Democrat Biden shot back.

But Ryan quickly turned to dreary economic statistics - 23 million are struggling to work, he said, and 15 percent of the country is living in poverty. "This is not what a real recovery looks like."

Medicare was a flashpoint, as well. Ryan said Obama's health care plan had diverted $716 billion from the program for seniors and created a new board that could deny care to patients who need it.

Democrats "haven't put a credible solution on the table," he said. "They'll tell you about vouchers. They'll say all these things to try to scare people."

Biden quickly said that Ryan had authored not one but two proposals in which seniors would be given government payments that might not cover the entirety of their care. Otherwise, he said, the Romney-Ryan approach wouldn't achieve the savings they claimed.

Unlike Obama, Biden had no qualms about launching a personal attack on Romney.

After Ryan argued that Romney's plan would pay for reduced tax rates by eliminating tax loopholes for the wealthy, Biden noted that on a recent interview on CBS' "60 Minutes," Romney defended the 14 percent tax rate he pays on his $20 million income as fair, even though it's a lower rate than some lower income taxpayers pay.

"You think these guys are going to go out there and cut those loopholes," Biden asked, addressing the national TV audience.

Across 90 minutes, the two men agreed precisely once.

That was when Ryan, referring to the war in Afghanistan, said the calendar was the same each year. Biden agreed to that, but not to the underlying point, which was that it was a mistake for Obama to have announced a date for the withdrawal of the remainder of the U.S. combat troops.

The fiercest clash over foreign policy came in the debate's opening moments, when Ryan cited events across the Middle East as well as Stevens' death in Libya as evidence that the administration's foreign policy was unraveling. The Republican also said the administration had failed to give Stevens the same level of protection as the U.S. ambassador in Paris receives.

Biden rebutted by saying that the budget that Ryan authored as chairman of the House Budget Committee had cut the administration's funding request for diplomatic security by $300 million.

On the nation's economy, both men were asked directly when his side could reduce unemployment to 6 percent from the current 7.8 percent. Both men sidestepped.

Biden repeated the president's contention that the nation is moving in the right direction, while Ryan stated the Republican view that economic struggle persists even though Democrats had control of both houses of Congress during the first two years of Obama's term.

"Where are the 5 million green jobs" we were told would be created? Ryan said to Biden.

For Biden, Thursday night's debate was his first since the 2008 campaign, when he shared a stage with Sarah Palin, then John McCain's running mate.

Ryan spars frequently with Democrats during debates on legislation on the House floor and in the House Budget Committee, which he chairs, but not in a one-on-one encounter covering 90 minutes and a virtually unlimited range of topics.

For all their differences, the two men shared a common objective, to advance the cause of their tickets in a close race for the presidency - and avoid a gaffe that might forever seal their place in the history of debates.

Both Ryan and Biden held extensive rehearsals, with stand-ins for their opponents.

Biden turned to Rep. Chris Van Hollen, D-Md., who is well-versed in Ryan's policy views from his tenure as senior Democrat on the Budget Committee.

Ryan's foil in rehearsal was former Solicitor General Ted Olson, a skillful courtroom advocate.

VIDEO: Vice presidential debate