A little free advice for presumptive Democratic presidential nominee John Kerry: Criticizing your opponent works better when you have your facts straight.

For instance, Sen. Kerry says he's going to stop the Bush administration's research on a new generation of nuclear weapons because "this is a weapon that we don't need."

The problem with this statement? The Bush administration is not researching or developing any new nuclear weapons. It is studying what armaments our military might need to keep us safe in the future -- something most Americans would consider prudent. The nation's finest strategic thinkers are on the case, and they haven't yet decided what the military of the future should look like, let alone what weapons it will require. So, it's a bit premature to declare which future weapons "we don't need."

To be fair, those strategic thinkers very well could recommend significant changes to our nuclear forces. They likely will be much smaller and consist of a greater variety of weapons. Our nuclear forces did end World War II, kept the Cold War cold and likely deterred Saddam Hussein from using chemical or biological weapons in the first Gulf War. But the threats have changed, and we can't assume those weapons will be as effective in the future.

During the Cold War, the United States regularly modified its nuclear arsenal to reflect its evolving relationship with the Soviet Union. These modifications helped keep the Soviets from using their nukes against us. But today, even acknowledging that nuclear weapons still have a role to play in our country's defense -- not to mention studying what that role should be -- has become politically charged. Sen. Kerry's comments -- coming before any new weapon has been suggested, let alone designed -- hardly advance this debate.

Worse, these comments come at a time when the world seems to grow more dangerous by the day. Proliferation of nuclear weapons is advancing at a dangerous pace. China has begun a nuclear modernization program. India and Pakistan have tested nuclear weapons. Nations such as Iran and North Korea have edged closer to becoming nuclear states. And even non-state actors -- terrorists, such as Osama bin Laden -- can become nuclear players if they find the right seller.

The Cold War provided much more stability than today's environment. Self-preservation truly motivated the Soviets. They didn't attack us because they didn't want us to respond. But Cold War deterrence is wholly inadequate in today's dangerous and chaotic world, especially when dealing with people willing to die to attack us.

What deters those people and the states that harbor them? What role do nuclear weapons play in this?

Questions such as these prompted the Bush administration to begin to re-evaluate the role of nuclear weapons in national security policy and to examine what experts call "low-yield" nukes -- weapons that can perhaps wipe out an enemy's headquarters buried deep underground, without leveling the entire city overhead. We still need traditional weapons to counter adversaries with large land forces that could overrun our expeditionary forces. But the new threats emerging require new approaches.

Future enemy leaders may not even regard our nuclear arsenal as a threat. And you deter no one unless you present a credible threat. Americans have demonstrated a reluctance to kill innocent people, and it would be nearly impossible to unleash even one of our present stock of nukes without killing hundreds of thousands -- if not millions -- of innocents.

Also, thanks to our overwhelming advantage in information technology, America, in many cases, can overwhelm an enemy force before our troops come within range of its weapons.

Our enemies are adjusting to this by moving their operations underground. Until conventional weapons and/or forces can be developed to destroy these underground targets, the United States should consider developing low-yield tactical nuclear weapons for this purpose.

It would be nice if we never had to consider the notion of war in the future. But it would not be realistic.

President Bush is right to start asking the question: What next? Sen. Kerry is wrong to pretend he already knows the answer.

Jack Spencer is a senior policy analyst for defense and national security at The Heritage Foundation.