The United States Wednesday charged the Soviet Union with posing a threat to Pakistan by sending SS1 Scud missiles to Afghanistan. The accusation was coupled with a veiled warning that the United States is determined to protect Pakistan. "The Soviet Union knows the government of Pakistan enjoys our support," Charles E. Redman, the State Department spokesman, said. The U.S. official said Pakistan was within range of the missiles. The United States has reserved the right to provide guerrillas fighting the Afghan government with equal firepower. Redman declined to say whether that step would be taken.