Imposition of martial law in Poland had been seriously considered in Moscow and Warsaw long before the step was taken early Dec. 13, East European sources in Moscow say.
Last spring, Soviet officials let it be known privately that one Kremlin option on the Polish crisis was to press for imposition of martial law or the declaration of some form of national emergency. In September, the sources say, the issue came up again. This time the pressure is said to have come from senior Polish military men. They reportedly told then-Communist Party chief Stanislaw Kania that he had to crack down, and that if he didn't, they would.
Gen. Wojciech Jaruzelski replaced Kania as party head in October.
The sources predict that one early priority of the new martial law regime will be to overhaul what it sees as a ''weak'' party structure. But the timing and success of this and other moves are seen as dependent on the still-uncertain course of events in Poland.