Kissinger, speaking Monday at George Washington University along with four other former U.S. State Department secretaries, said the next president should initiate high-level discussions with Iran "without conditions," ABC News reported.

The opinion of the former secretary of state for Republican presidents Richard Nixon and Gerald Ford differs sharply with that of the current GOP administration, which has maintained a strict policy of not negotiating directly with governments deemed to sponsor international terrorism. The Bush administration has demanded that Iran dismantle its nuclear program as a precondition for any direct talks.

The other former secretaries of state, Madeleine Albright, James Baker III, Warren Christopher and Colin Powell, were asked to identify the biggest challenges the next president will face. They answered the fight against terrorism, restoring America's reputation abroad, r-building U.S. economic power and global climate change, ABC reported.