There has been no national security issue that has preoccupied the presidency of George W. Bush more than the threat of weapons of mass destruction falling into the hands of terrorists. But Wednesday, a congressionally-mandated bipartisan commission is slated to deliver a sobering report to the White House concluding that the threat is as great as ever—and that it is now better than 50-50 that a WMD terrorist attack will take place someplace in the world in the next five years. In an interview with NEWSWEEK, commission co-chair Bob Graham—former chairman of the Senate Intelligence Committee and a senior advisor on intelligence issues to Barack Obama's transition team—discusses the panel's work.

NEWSWEEK: Is there something you learned in the course of working on this that surprised you?
Bob Graham: Yes. What surprised me was the degree of risk associated with a biological weapon. When you think weapons of mass destruction, you tend to think mushroom cloud. But the ubiquitous nature of pathogens and the increasing lethality of both natural and synthetic pathogens led our commission to conclude it's more likely that an attack will come biologically rather than nuclear.

Give me an example of the kind of attack you ' re referring to.
Today, the focus is on anthrax. Anthrax is a naturally produced pathogen that comes from dead cattle. But in current life sciences, maybe an even greater threat is posed by the ability to create new—or to resurrect older—pathogens. As an example, the influenza of 1918, which killed 40 million people. That particular pathogen had been extinct [in the years after the 1918 epidemic] until it was re-created in a laboratory. Should that fall into the hands of evil people with the appropriate capability for organization and technical dissemination, it could exceed the lethality of 90 years ago. I would say that's my worst nightmare.

You start out the report by saying there is a better than even chance there will be such an attack by the end of the year 2013. A lot of people are wondering , where do you get that? How reliable is something like that?
We interviewed over 250 people—scientists, academics, military, political personnel from the United States and other countries as well as visiting research facilities in the United States and abroad. And the nine members of the commission, most of whom have a background in these areas, reached [that] unanimous conclusion.

Rep. Jane Harman issued a press release today suggesting the commission is playing the " fear card " here, that this is the kind of talk we ' ve heard from the Bush administration in recent years — and maybe a little too much of that distorts the debate ?
This issue has been stated by every presidential candidate at least going to back to the year 2000 as being the No. 1 security concern for the United States—including [President-elect] Barack Obama. The problem is, while we have done some things that have reduced the threat, we haven't done enough. Our adversaries are gaining greater capabilities and our margin of safety has been retreating. There has been a series of policy issues in which proliferation was posited against either an economic or a geopolitical objective. And in the large majority of those cases, proliferation has lost. The most recent example of that is the Indian nuclear agreement, [allowing for the sale of U.S. nuclear technology to India] which has a very destabilizing effect on nonproliferation treaty commitments. China has cited the India agreement when it sold reactors to Pakistan. Russia has cited it in defense of its relations with Iran. So our action has contributed to our greater vulnerability.

That should make things interesting when you present the report to the president tomorrow.
We felt we should not pull any punches. Our report would indicate we have less than 1900 days [before] it is more likely than not that a weapon of mass destruction will go off someplace in the world.