NATO did not immediately confirm that it had carried out the missile attack that killed Seif al-Arab Gadhafi, 29. Regime officials said that Moammar Gadhafi and his wife were visiting the home when it was struck, but both were unharmed.
Gadhafi's youngest son's death comes one day after the Libyan leader appeared on state television calling for talks with NATO to end the airstrikes, which have been hitting Tripoli and other Gadhafi strongholds since last month.
Western officials have been divided in recent weeks over whether Gadhafi is a legitimate military target under the United Nations Security Council resolution that authorized the air campaign. Defense Secretary Robert Gates said last week that NATO was "not targeting Gadhafi specifically" but that his command-and-control facilities -- including one inside his sprawling Tripoli compound that was hit with airstrikes last Monday -- were legitimate targets.
The Pentagon also wouldn't confirm the airstrike Saturday.
The Obama administration is said to believe that killing Gadhafi under the current conditions would exceed the UN mandate, which calls for airstrikes to protect civilians.
U.S. officials rejected an assertion last month by Gates' British counterpart, Liam Fox, who said that assassinating Gadhafi was "potentially a possibility."
Before the strike, NATO brushed aside Gadhafi's call for a truce and negotiations to end the international bombing campaign, and alliance warships cleared sea mines laid by his forces near the harbor of the only major city held by rebels in western Libya.
Three aid ships were prevented from docking at the port of Misrata during the sweep, temporarily cutting off the besieged city of 300,000 people from its only lifeline.
In a predawn speech, Gadhafi said, "The door to peace is open." "You are the aggressors. We will negotiate with you. Come, France, Italy, UK, America, come to negotiate with us. Why are you attacking us?"
In Brussels, a NATO official said the alliance needed "to see not words but actions," and vowed to keep up the pressure until the UN Security Council mandate on Libya is fulfilled.
The NATO official, who spoke on condition of anonymity according to policy, noted that Gadhafi's forces had shelled Misrata and tried to mine the city's port just hours before his speech.