The meeting at Offutt Air Force Base in Nebraska, the headquarters of U.S. Strategic Command, was to feature senior civilian and military Pentagon officials, as well as representatives of the Department of Energy's National Nuclear Security Administration, the National Security Council, the State Department, and the departments of the Air Force and Navy.
It comes amid signs of possible changes in U.S. nuclear policy.
Congress is debating whether to allow research on low-yield nuclear weapons. A recent U.S. strategy review identified new countries where "contingencies" might involve nuclear weapons. At the same time, the U.S. and Russia have agreed to historic reductions in their stockpiles of warheads.
Maj. Michael Shavers, a Defense Department spokesman, said Thursday's meeting at Offutt would discuss several key issues, starting with how to make sure the country's nuclear weapons are reliable.
The U.S. conducted its last nuclear test in 1992. Shavers said Thursday's meeting will consider "How do you continue to maintain that usefulness, that efficacy, without engaging in nuclear testing?"
While the White House opposes the Comprehensive Test Ban Treaty — which the U.S. has signed but not ratified — the administration says it has no plans to conduct a test.
However, a leaked version of an agenda for Thursday's meeting — one made public early this year by an anti-nuclear advocacy group — indicates it will include discussion of the question: "What is the uncertainty in confidence and potential risk threshold for a test recommendation—what would demand a test?"
Defense officials have expressed concerns about how long it would take the United States to conduct a test if it became necessary.
Shavers could not comment on the specifics of the planned discussion of testing.
Thursday's meeting will also address the Moscow treaty, signed by President Bush and Russian President Vladimir Putin last May, in which the two sides pledged to slash their active arsenals within 10 years by nearly two-thirds, to 1,700 to 2,200 warheads each.
"How do you accomplish this while maintaining a credible nuclear deterrent?" is a question the meeting will consider, said Shavers.
The Offutt meeting will also consider the implications of last year's Nuclear Posture Review.
According to a leaked version of the review, the administration identified Iraq, Iran, Syria, Libya, North Korea as countries where "contingencies" could arise for which U.S. "nuclear strike capabilities" must be prepared.
"We need to adjust our nuclear strategy from a Cold War strategy to a strategy to deal with…emerging threats," Shavers said.
The leaked agenda for Offutt indicates the meeting will also discuss low-yield weapons and earth penetrating nuclear bombs, two issues that Congress is also debating.
Shaver says the potential for those new weapons is "just one of many things that's going to be on the table."
Low-yield weapons are nuclear bombs of less than five kilotons and might be useful for destroying stockpiles of weapons of mass destruction. Earth-penetrating bombs could destroy deep bunkers that the administration claims terrorists might use for shelter.
Congress is considering overturning a 1993 ban on research or development of low-yield weapons. Some Democrats oppose lifting the ban, saying it sends the wrong message at a time when the U.S. has made nonproliferation a top foreign policy objective.
Both Houses of Congress have advanced measures lifting the ban on research but maintaining the prohibition of any actual development of low-yield weapons.
For the second year in a row, the Energy Department is requesting $15 million to study the need for a Robust Nuclear Earth Penetrator. The House appears poised to grant a smaller amount.
In April the United States produced a weapons-grade plutonium pit — the core of a fission bomb — for the first time in 14 years.
According to the Los Alamos National Laboratory, the move "restores the nation's ability to make nuclear weapons," and was needed so the Energy Department could replace pits found unsafe or destroyed through regular check-ups.
According to Shavers, the outcome of Thursday's meeting will be a report to the departments of Defense and Energy, possibly outlining the content of the discussions, research questions going forward and other issues.
By Jarrett Murphy