TEHRAN — Iran’s vice president delivered a baldly anti-Semitic speech on Tuesday at an international antidrug conference here, saying that the Talmud, a central text of Judaism, was responsible for the spread of illegal drugs around the world.

European diplomats in attendance expressed shock. Even Iranian participants in the conference, co-sponsored by Iran and the United Nations, privately wondered at their government’s motive for allowing such a speech, even given its longstanding antagonism toward Israel. More than 25,000 Jews live in Iran, and they are recognized as a religious minority, with a representative in Parliament.

The speech by Vice President Mohammad-Reza Rahimi seemed bound to isolate Iran further just days before a new set of onerous Western economic sanctions, notably a European embargo on Iranian oil, is set to be enforced because of the longstanding dispute over Iran’s nuclear program. Iran says the program is peaceful, and Western nations and Israel suspect it is a cover to develop the ability to make nuclear weapons.

Mr. Rahimi, second in line to President Mahmoud Ahmadinejad, said the Talmud teaches to “destroy everyone who opposes the Jews.”