I doubt the Soviets would want to. An intervention would only lead to American counter-intervention in support of the coup, and escalate the whole affair. The Chilean UP government was never really that close to the USSR anyway for the Soviets to care enough. The best chance to end the coup militarily would have been to have a non-military armed force ready to defend the government against a coup, like a Spanish-civil-war type militia. IIRC there were actually some suggestions about creating something like this in the weeks leading up to the coup, but Allende rejected the idea.