The Republicans have raised sharp questions over the administration's handling of the security and protection of US facilities and personnel overseas.

Thursday's vice presidential debate will not decide the outcome of the November 6 showdown, but still matters in this close election, said Brookings Institute fellow Elisabeth Jacobs on Wednesday during a web chat.

"Debates can change the polls, but typically not in a fundamental way that decides the election," said Jacobs.

She expected Biden and Ryan to try to bring up issues which they have strong history in. Biden is expected to bring up foreign policy and women issues while Ryan is expect hammer the deficit issue.

The 69-year-old vice president, a former chairman of the Senate Foreign Relations and Judiciary Committees, is expected to highlight the Romney-Ryan ticket's lack of international experience during the debate.

The 42-year-old Ryan, a seven-term congressman and chairman of the House of Representatives Budget Committee, is a leading figure outlining the Republican party's budget plan.

Vice presidential debates traditionally don't carry the same influence as presidential debates in elections. But stakes have been raised for both campaigns over the 90-minute debate on Thursday evening.

After Obama's lackluster performance in the first presidential debate with Republican nominee Mitt Romney last week, Biden is under pressure to do well in this debate.

For Romney's side, another win could help the Romney-Ryan ticket hold the momentum heading into the November showdown.

Ahead of the debate, campaign spokeswoman Jen Psaki told reporters on Thursday that Biden "is pretty fired up and ready to go this evening for the debate."

The latest Pew survey released on Wednesday found that voters are divided over who will do better in Thursday's vice presidential debate, with 40 percent expecting Ryan to be the winner and 34 percent favoring Biden.