Top Bush and Clinton administration officials are appearing Tuesday before a special commission investigating the September 11, 2001, terrorist attacks.
Former U.S. Secretary of State Madeleine Albright said the United States owes it to the families of the victims to do everything it can to prevent future attacks.
Secretary of State Colin Powell and Defense Secretary Donald Rumsfeld are among the officials scheduled to give testimony at open hearings of the National Commission on Terrorist Attacks Upon the United States, popularly known as the 9/11 Commission. The commission says the hearings will focus on the conduct of U.S. counter-terrorism, particularly during the period from the August 1998 embassy bombings in Kenya and Tanzania to September 11, 2001. It is probing why U.S. intelligence failed to prevent the attacks that killed more than 3,000 people.
The commission's work is especially sensitive amid the presidential campaign, in which Mr. Bush is highlighting his role as a wartime president.
Meanwhile, the Bush administration is strongly rejecting accusations from former White House counter-terrorism official Richard Clarke that it ignored the al-Qaida threat in the months leading up to the attacks on the World Trade Center and the Pentagon.
In a book released Monday, Mr. Clarke says the president urged him to look for a connection between the terrorist attacks and former Iraqi leader Saddam Hussein, although there was no evidence such a link existed. Mr. Clarke said the president should have focused more on al-Qaida. He says the war in Iraq was unnecessary and costly, and it has made the country less safe and strengthened Islamic militant organizations.
Former Clinton administration Defense Secretary William Cohen will also testify before the nine-member bi-partisan commission, as well as Mr. Clarke - who served as President Clinton's "terrorism-czar."
Central Intelligence Agency Director George Tenet will appear on Wednesday. National Security Advisor Condoleezza Rice has declined to testify publicly before the commission, but she has already testified privately before some commission members.
Some information for this report provided by Reuters, AFP and AP.