WASHINGTON - The Bush administration will inform Congress today that Israel may have violated agreements with the United States when it fired U.S.-supplied cluster munitions into southern Lebanon during its fight with Hezbollah last summer, the State Department said.

The finding, though preliminary, has prompted a contentious debate within the administration over whether the United States should penalize Israel for its use of cluster munitions against towns and villages where Hezbollah had placed its rocket launchers.

Cluster munitions scatter tiny but deadly bomblets that explode over a wide area. The grenadelike munitions, tens of thousands of which have been found in southern Lebanon, have caused 30 deaths and 180 injuries among civilians since the end of the war, according to the U.N. Mine Action Service.

Mid-level officials at the Pentagon and the State Department have argued that Israel violated U.S. prohibitions on using cluster munitions against populated areas, according to officials who described the deliberations. But other officials in both departments contend that Israel's use of the weapons was for self-defense and aimed at stopping the Hezbollah rocket attacks that killed 159 Israeli citizens and at worst was only a technical violation.

Any sanctions against Israel would be an extraordinary move by the Bush administration, a strong backer of Israel, and several officials said they expected little further action, if any, on the matter.

The State Department is required to notify Congress even of preliminary findings of possible violations of the Arms Export Control Act, the statute governing arms sales. It began an investigation in August.

Sean McCormack, the State Department spokesman, said on Saturday that the notification to Congress would occur today but that a final determination about whether Israel violated the agreements on use of cluster bombs was still being debated.

"It is important to remember the kind of war Hezbollah waged. They used innocent civilians as a way to shield their fighters," he said.

Even if Israel is found to be in violation, the statute gives President Bush discretion about whether to impose sanctions, unless Congress decides to take legislative action. Israel makes its own cluster munitions, so a cutoff of U.S. supplies would have mainly symbolic significance.

Israel gave the State Department a dozen-page report late last year in which it acknowledged firing thousands of U.S. cluster munitions into southern Lebanon but denied violating agreements that prohibit their use in civilian areas, the officials said.

Before firing at rocket sites in towns and villages, the Israeli report said, the Israeli military dropped leaflets warning civilians of the attacks. The report, which has not previously been disclosed, also noted that many of the villages were deserted because civilians had fled the fighting, the officials said.

Human Rights Watch in October reported that Hezbollah had fired cluster munitions into northern Israel.