Mr. Assad also made his first public comment on the airstrike, saying on Sunday that Syria would confront any aggression against his country, according to The Associated Press.

The ease with which Israeli planes reached the Syrian capital appeared to send a message both to Mr. Assad and, indirectly, to Iran.

Israel has said that if it saw chemical weapons on the move, it would act to stop them. By hitting the research center, part of a military complex that is supposed to be protected by Russian-made antiaircraft defenses, Israel made it clear it was willing to risk direct intervention to keep weapons and missiles out of Hezbollah’s hands.

Israel has done so before, in September 2007, when it destroyed a Syrian nuclear reactor that was under construction with North Korean help. The facility hit last week was also believed to be a center for study on nuclear issues, officials say.

But there are reasons to doubt whether the antiaircraft equipment was truly heading to Hezbollah. Outside experts like Ruslan R. Aliyev, an analyst with the Center for the Analysis of Strategy and Technologies, a defense research group in Moscow, said the SA-17’s were too sophisticated for Hezbollah to use and would be easily detected. He also said such a transfer would alienate Russia and make it impossible for Moscow to sustain its support for Mr. Assad’s government.

The strike last week also appeared to be a signal to the Iranians that Israel would be willing to conduct a similar attack on aboveground nuclear facilities if it seemed that Iran was near achieving nuclear weapons capability. But Iran would be a far harder target — much farther away from Israel, much better defended, and with facilities much more difficult to damage.

The nuclear enrichment center that worries Israel and Western governments the most is nearly 300 feet under a mountain outside Qum, largely invulnerable to the weapons that Israel seemed to have used in last week’s raid.