"I think when the question arises and when there is felt to be the need that there's information that only the president might have, that's when that question will arise and that's when we will pursue the facts with the leaders," Kissinger said during an appearance on CNN's "Late Edition."
Kissinger and former Sen. George Mitchell spoke out on Sunday's talk shows about the commission they will lead, which has been charged with examining the events leading up the Sept. 11, 2001, terrorist attacks on New York and Washington that killed nearly 3,000 people.
The two men said they would determine which U.S. or foreign leaders they would question as work on the panel developed.
"This will come up in the ordinary course of events, and we will deal with it at that time, as with foreign leaders, as with the president, as with anybody else involved," Mitchell said. "But we're not going to make decisions at this point on our own about how we're going to proceed until we follow the law, get the commission established and get into the process."
Washington officials have blamed Saudi fugitive Osama bin Laden and his Islamic extremist group al Qaida for the attacks. The commission will seek answers about possible failures in intelligence and border security that could have allowed the attacks to occur.
Bush appointed Kissinger, who served under both presidents Richard M. Nixon and Gerald Ford, to head the 10-person panel. Mitchell, a Democrat, will serve as vice chairman. Mitchell has been working with the White House in the effort to broker a peace deal between the Israelis and Palestinians.
The commission will determine whether the United States or other governments had information that could have prevented the attacks and whether anything could have been done to avert the tragedy.
The commission will have 10 members, including Kissinger and Mitchell. The remaining eight members must be appointed by Dec. 15 -- half by Democrats, half by Republicans -- for the investigation expected to last about 18 months.
Mitchell promised a "complete, fair, nonpartisan" inquiry into the attacks. He said he was confident he would have access to the information and individuals the panel would need to carry out its investigation. The panel would have subpoena powers, but both Mitchell and Kissinger declined to say whom they would call as witnesses.
"It would be insulting in the extreme to the other eight persons (on the commission) and presumptuous on our part for Dr. Kissinger and I now to announce who we're going to question and what we are going to do. We ought to, obviously, solicit the views of the other commissioners on any major substantive issue," Mitchell said.
Kissinger responded to criticism that Bush appointed him to soften the intensity of an investigation to which White House was initially opposed. He said that Bush told him he was committed to getting the facts and circumstances and that the commission should make recommendations that he would be eager to review.
Last week, Bush said "The sooner we have the commission's conclusions, the sooner this administration will act on them" and urged the panel act independently.
"This investigation should carefully examine all the evidence and follow all the facts, wherever they lead. We must uncover every detail and learn every lesson of September the 11th," Bush said.
Both Mitchell and Kissinger deflected criticism that their possible business links to foreign governments that could impede a fair and impartial investigation. Kissinger said that while no law firm discloses its client list, he would discuss his clients fully with White House counsel and "appropriate ethics groups."
"The possibility that the investigation of a commission that contains eight commissioners would be affected by any conceived commercial interests is outrageous. I have served six presidents and I have never been accused of anything of this kind," Kissinger said.
Mitchell said he has had to disclose any clients that may have activity with the federal government under federal lobbying laws. He said he would disclose any such ties "as needed."