State Department spokesman Kurtis Cooper said Saturday the report will be forwarded to Congress on Monday, but declined to disclose the findings, emphasizing that they are preliminary.
"The Israeli government is also taking quite seriously their responsibility in providing information," Cooper said. "We are not making a final judgment."
The State Department is required to notify Congress of even preliminary findings of possible violations of the act cited by Cooper.
The New York Times reported on its Internet site Saturday evening that the report will say Israel may have violated agreements with the United States by its use of American-supplied cluster munitions during last year's war.
The paper described disagreement among midlevel officials at the Defense Department and the State Department, with some in both departments arguing that Israel violated U.S. prohibitions on using cluster munitions against population areas. Others in both departments argued that the weapons were used in self-defense to stop Hezbollah rocket attacks and that, at worst, only a technical violation may have occurred.
A congressional investigation found Israel improperly used U.S.-made cluster bombs during its 1982 invasion of Lebanon. Then-President Ronald Reagan's administration then imposed a six-year ban on further sales of the weapons to Israel.
Such sanctions are largely symbolic, however, since Israel also makes its own cluster munitions.
The United Nations said unexploded cluster bombs — anti-personnel weapons that spray bomblets over a wide area — litter homes, gardens and highways in south Lebanon.
Relief organizations and the U.N. mine office have reported finding evidence that Israel used three types of U.S.-made cluster bombs during the 34-day war with Hezbollah militants, during which both sides fired rockets into populated areas.
The U.N. mine office has said it had found hundreds of bomblets of the types made by the United States among unexploded ordnance recovered in nearly 250 locations in southern Lebanon.
The Israeli army has said all weapons it uses "are legal under international law and their use conforms with international standards."
Cluster bombs are typically used against tanks and explode upon impact with steel. In the conflict in Lebanon, the shells were fired into urban and rural areas where Israel thought Hezbollah guerrillas might be hiding. Many hit the ground or pavement and did not explode.
Israel said it was forced to hit civilian targets in Lebanon because Hezbollah fighters were using villages as bases for rocket launchers aimed at Israel. At least 850 Lebanese and 157 Israelis died in the fighting.
The Bush administration repeatedly warned Israel to avoid civilian casualties during the cross-border war, but refrained from direct criticism of Israeli tactics.