Israel may have violated an agreement with Washington by using American-made cluster bombs during last summer's war with Hezbollah guerrillas in Lebanon, the U.S. State Department said Monday.

White House spokesperson Sean McCormack said a preliminary report on an American probe into the issue has been handed to Congress, but didn't provide further details on the investigation.

"There were likely violations," McCormack told reporters.

The probe was opened in 2006 after UN reports that three types of American cluster bombs were found in populated areas in southern Lebanon.

Cluster bombs release smaller bomblets that spread out on the ground.

The report, McCormack said, "is not a final judgment." He declined to speculate on what action may be taken against Israel if a violation is confirmed.

When Israel purchases cluster bombs and other lethal equipment from the United States, it must agree in writing to restrictions on their use, including using them in civilian areas.

The Israeli army has said all weapons it uses "are legal under international law and their use conforms with international standards."

The UN has called for a freeze on their use in or near populated areas.