In a joint television interview, the chair and vice chair of the 9/11 Commission indicated Sunday that the panel has gathered evidence that shows the Sept. 11 attacks probably could have been prevented.

The vice chairman, Lee Hamilton, said, “There are a lot of ifs; you can string together a whole bunch of ifs, and if things had broken right in all kinds of different ways, as the governor has identified, and frankly if you’d had a little luck, it probably could have been prevented.”

The chair of the commission, Thomas Kean, also warned Sunday he could not guarantee the panel’s report will be released before the presidential election because of a protracted White House vetting process.

In related news, the Bush administration reversed itself on Friday and said the 9/11 Commission would be allowed to view thousands of classified documents handed over by President Clinton. It is not clear if the commissioners will be allowed to keep copies of the documents or if they will be allowed only to view the papers.