The officials, who spoke on the condition of anonymity, identified the victim as an Iraqi named Abu Ghadiya and said he had eluded U.S. forces for years.
Anthony Cordesman, a military expert at the Center for Strategic and International Studies in Washington, said the smuggler also went by the name of Sulayman Khalid Darwish and that another senior smuggler was captured.
While Syria has cracked down on foreign fighters in recent years, Syria is "still the key source of support for al Qaeda in Iraq," Mr. Cordesman said. "Jordan and Saudi Arabia have done a pretty good job of keeping things under control, but the rat lines still go through the Syrian border."
"It's a matter of getting a window of opportunity," a U.S. military official said. "When it comes to top al Qaeda leaders, in general, either you act when you get information, or you lose them."
Syrian officials strongly protested the attack, which they said killed eight people, including women and children, in the village of Sukkariyeh, about five miles from the border with Iraq.
Syrian Foreign Minister Walid al-Moallem called the raid an act of "criminal and terrorist aggression."
State Department spokesman Sean McCormack said the Syrian government called in the senior U.S. diplomat in Damascus, Maura Connelly, to complain about the violation of Syrian territory.
According to the Syrians, four U.S. military helicopters attacked a civilian building under construction shortly before sundown Sunday.
The Associated Press quoted a Sukkariyeh resident, who spoke on the condition of anonymity because he said he feared for his life, as saying that he saw at least two men taken into custody by American forces. Another villager showed amateur video footage on his mobile phone of four helicopters flying toward them as villagers point to the skies in alarm.
An AP journalist who saw the grainy video said it also showed the floor of the targeted building. White tennis shoes on the floor were surrounded by blood and pieces of human flesh. A tent pitched near the site had bags of bread, pots and pans and wool blankets.
In recent weeks, U.S. strikes against al Qaeda leaders and top commanders have increased in frequency in Iraq, Afghanistan and Pakistan. According to several top military and intelligence officials, the attacks are intensifying owing to better intelligence and the Bush administration's desire to kill or capture al Qaeda leader Osama bin Laden before President Bush leaves office.
However, in some cases the strikes have led to the deaths of civilians. A senior Pakistani senior official, who spoke on the condition that he not be named, said these intelligence failures have "played into the hands of al Qaeda and the Taliban."
Mr. McCormack declined comment on the incident, apart from saying that "all the way back to 2001, the United States and its friends and allies around the world have had to do difficult things in the war on terror ... ."
"This is a tough fight ... ," he said. "And like I said, you have to come at the problem ... across a variety of different fronts."