Democratic presidential candidate Barack Obama (web|news|bio) called on two potential running mates and a host of foreign policy experts Wednesday as he pushed his agenda for Iraq (web|news) and his views for U.S. foreign policy elsewhere. Sen. Evan Bayh, D-Ind., and former Sen. Sam Nunn, D-Ga., were scheduled to join Obama for a national security roundtable at Purdue University in West Lafayette, Ind. "Sen. Obama understands that the threats we face in a 21st century go far beyond the wars of today," the Obama campaign said in a statement. "In order to be fully prepared, we must begin to implement effective strategies now that reduce the risk of three particularly catastrophic events - a nuclear attack, a biological attack or a cyber attack."

The event continued the buildup for Obama's upcoming visit to Iraq and Afghanistan. He also plans to visit Jordan, Israel, Germany, France and Britain during his overseas trip. Visiting Purdue also brings Obama back to Indiana, a pivotal electoral state.

Bayh has demurred when asked about running on a ticket with Obama. Nunn, a defense expert, is viewed as a senior statesman who could offset the relative youth of Obama, a freshman senator.

Also expected to join the discussion at Purdue were Graham Allison, a nuclear nonproliferation specialist and former dean of the Kennedy School of Government; two specialists on bio security, Tara O'Toole of the Center for Bio Security at the University of Pittsburgh and Dr. David Relman of Stanford University Medical School; and two cyber security specialists, Paul Kurtz, a former senior member on the National Security Council and Homeland Security Council, and Alan Wade, former chief information officer for the CIA.