Regarding Steve Coll's Feb. 6 Outlook piece, "What Bin Laden Sees in Hiroshima":

It is not a lack of nuclear expertise keeping terrorists such as Osama bin Laden from acquiring atomic weapons; it is the availability of fissile material and the precisely manufactured hardware and conventional explosives needed to detonate that material that frustrates them.

The theoretical know-how for making atomic weapons has been available for decades to physicists and their students worldwide. This is why deterrence is the critical factor in protecting the United States from a nuclear attack by terrorists. Only nation-states -- or heavy industries subject to national governments -- have the capability to produce the component parts of a nuclear device, a situation that is unlikely to change anytime soon. A terrorist group would have to purchase or otherwise acquire a completed weapon (or parts) from a government or agents of a government.

While preventing proliferation is good policy, too, the best way to forestall nuclear terrorism is to make sure that potentially hostile nuclear-capable nations such as Iran, North Korea and Pakistan understand that a nuclear attack on the United States would bring overwhelming retaliation against any suspected supplier of nuclear material used in an attack on us. Such a policy should encourage those countries to keep nuclear materials out of the hands of terrorists.

JONATHAN F. KEILER

Bowie