In his only public comment on the raid, Syria’s president, Bashar al-Assad, acknowledged this month that Israeli jets dropped bombs on a building that he said was “related to the military” but which he insisted was “not used.”

A senior Israeli official, while declining to speak about the specific nature of the target, said the strike was intended to “re-establish the credibility of our deterrent power,” signaling that Israel meant to send a message to the Syrians that even the potential for a nuclear weapons program would not be permitted. But several American officials said the strike may also have been intended by Israel as a signal to Iran and its nuclear aspirations. Neither Iran nor any Arab government except for Syria has criticized the Israeli raid, suggesting that Israel is not the only country that would be disturbed by a nuclear Syria. North Korea did issue a protest.

The target of the Israeli raid and the American debate about the Syrian project were described by government officials and nongovernment experts interviewed in recent weeks in the United States and the Middle East. All insisted on anonymity because of rules that prohibit discussing classified information. The officials who described the target of the attack included some on each side of the debate about whether a partly constructed Syrian nuclear reactor should be seen as an urgent concern, as well as some who described themselves as neutral on the question.

The White House press secretary, Dana Perino, said Saturday that the administration would have no comment on the intelligence issues surrounding the Israeli strike. Israel has also refused to comment.

Nuclear reactors can be used for both peaceful and non-peaceful purposes. A reactor’s spent fuel can be reprocessed to extract plutonium, one of two paths to building a nuclear weapon. The other path — enriching uranium in centrifuges — is the method that Iran is accused of pursuing with an intent to build a weapon of its own.

Syria is known to have only one nuclear reactor, a small one built for research purposes. But in the past decade, Syria has several times sought unsuccessfully to buy one, first from Argentina, then from Russia. On those occasions, Israel reacted strongly but did not threaten military action. Earlier this year, Mr. Assad spoke publicly in general terms about Syria’s desire to develop nuclear power, but his government did not announce a plan to build a new reactor.

The Gulf Cooperation Council, a group of Persian Gulf states, has also called for an expansion of nuclear power in the Middle East for energy purposes, but many experts have interpreted that statement as a response to Iran’s nuclear program. They have warned that the region may be poised for a wave of proliferation. Israel is believed to be the only nuclear-armed nation in the region.