After the British decided to bring the Palestine issue to the UN, Foreign Secretary Ernest Bevin’s adviser on Palestine asked a representative of the Jewish Agency why the Jews agreed to let the UN decide the fate of Palestine.“Don’t you know,” he said, “that the only way a Jewish state will be established is if the U.S. and Soviet Union agree? Nothing like that ever happened. It cannot possibly happen. It will never happen.”
In May 1947, however, Soviet delegate Andrei Gromyko said:
The fact that no Western European State has been able to ensure the defense of the elementary rights of the Jewish people and to safeguard it against the violence of the fascist executioners explains the aspirations of the Jews to establish their own State. It would be unjust not to take this into consideration and to deny the right of the Jewish people to realize this aspiration.
The principal reason the Soviets supported partition was their desire to see the British leave. They also hoped the new Jewish state would be pro-Soviet.
The Soviet Union backed partition and, subsequently, became the second nation to recognize Israel. While the British opposed partition in part because of their fear of the reaction of the Arabs, the Arabs never blamed the Soviets for their initial pro-Israel policy.
Sources: Zionism and Israel Center