"We support Israel's legitimate right to self-defense and continue to urge all parties to respect the blue line between Israel and Lebanon," State Department spokeswoman Jen Psaki told reporters.
She added that Washington condemned Hezbollah's shelling of an Israeli military convoy in an Israel occupied border area in which two Israeli soldiers were killed.
The US condemnation came shortly before the UN Security Council was to meet on the crisis in New York.
"We urge all parties to refrain from any action that could escalate the situation," Psaki said, adding Washington was closely monitoring the situation.