BEHIND KIEV'S FAREWELL TO ARMS

Many of the key changes that led to Ukraine's Jan. 10 agreement to give up the Soviet nuclear arsenal based within its borders involve a prominent role for the United States. The US, for example, will purchase the uranium from the warheads for use as fuel. As compensation, Ukraine will receive fuel for its power reactors. Russia and the US also will give joint guarantees of Ukraine's security.

The US met Ukrainian concerns by getting Moscow to agree to independent monitoring of the process of dismantling the warheads and turning them into fuel. Russia also ceded a key Ukrainian demand by agreeing to compensate Kiev, in the form of a debt write-off, for the uranium in tactical nuclear arms already removed from Ukraine.

The details of the deal are still under negotiation, and there is still a possibility that, like all the previous agreements, this too could fall apart.

One unresolved issue is the timetable. Moscow wants a three-year limit for removing the weapons. President Leonid Kravchuk seeks to avoid a specific deadline, though Ukraine has recommitted to the START arms reduction treaty, which has a seven-year term. The agreement also reportedly vaguely pledges to eliminate the ``most dangerous weapons'' first, a reference to the more modern SS-24 missiles.

Some Ukrainians link the timetable to events in Russia. ``Within a three-year period, it will be possible to monitor the changes in Russian democracy and adequately react to them,'' says former Defense Minister Konstantin Morozov.

Still, Ukrainian politicians are already attacking the deal. With elections set for spring, Mr. Kravchuk could face real trouble over his decision. ``It is a courageous decision,'' comments Vladimir Lukin, Russia's ambassador to the US. ``This decision corresponds to Ukrainian national interests, but it does not correspond to certain irrational ambitions.''