The federal commission investigating the Sept. 11 attacks will soon ask President Bush, former President Bill Clinton and their vice presidents to testify in public about possible warnings they might have received from U.S. intelligence sources before the attacks.

"We need them to testify," former New Jersey Gov. Thomas H. Kean (search), the bipartisan commission's chairman, told The Record of Bergen County. He said the panel would issue formal invitations within the next few weeks, although he conceded that all four men would probably decline to appear at a public forum where they could be asked questions.

However, Kean said their cooperation was "crucial" to the commission's work, so he hoped they would at least consent to private interviews with the panel.

Clinton has previously said that he would be willing to testify, and Bush said in a television interview last week that he might consider speaking with the panel.

However, a White House spokeswoman said Wednesday that she did not know whether Bush would agree to testify or be interviewed.

"I can't speculate on that," said Pamela Stevens, assistant White House press secretary. "We've given them [committee members] unprecedented access. We've worked in a very cooperative manner with them. We've given them 2.3 million documents, and we just continue to work with them in a cooperative manner."

Kean said the commission also plans to seek public testimony from Secretary of State Colin L. Powell (search), National Security Adviser Condoleezza Rice (search), Defense Secretary Donald Rumsfeld, CIA Director George Tenet, Attorney General John Ashcroft, and their counterparts in the Clinton administration.

In a related matter, Kean met behind closed doors Wednesday with relatives of those killed in the attacks. He came under tough questioning during the three-hour session from those concerned that the panel has been given too little time to finish its investigation and is prejudging its conclusions.

The meeting came a day after the panel announced a compromise deal with the White House over access to classified intelligence documents. Some of the family members were upset that the commission did not get full access to other important documents.

Patty Casazza of Colts Neck, N.J., whose husband died in the attacks, said the panel should press Congress to approve as much time as needed to thoroughly complete their work.

"I hope that the commission would stand with the families on the side of what is right and ethical as opposed to caving in to the political pandering in Washington," Casazza told The Star-Ledger of Newark. "I feel their decisions are being influenced by what they think they will be able to get out of Washington."