The United States had approved the sale of M-26’s to Israel some time ago, but the weapons had not yet been delivered when the crisis in Lebanon erupted. If the shipment is approved, Israel may be told that it must be especially careful about firing the rockets into populated areas, the senior official said.

Israel has long told American officials that it wanted M-26 rockets for use against conventional armies in case Israel was invaded, one of the American officials said. But after being pressed in recent days on what they intended to use the weapons for, Israeli officials disclosed that they planned to use them against rocket sites in Lebanon. It was this prospect that raised the intense concerns over civilian casualties.

During much of the 1980’s, the United States maintained a moratorium on selling cluster munitions to Israel, following disclosures that civilians in Lebanon had been killed with the weapons during the 1982 Israeli invasion. But the moratorium was lifted late in the Reagan administration, and since then, the United States has sold Israel some types of cluster munitions, the senior official said.

Officials would discuss the issue only on the condition of anonymity, as the debate over what to do is not resolved and is freighted with implications for the difficult diplomacy that is under way.

State Department officials “are discussing whether or not there needs to be a block on this sale because of the past history and because of the current circumstances,” said the senior official, adding that it was likely that Israel will get the rockets, but will be told to be “be careful.”