The contaminant has been linked to the deaths of more than 300 children in Africa and Asia
Police described the alleged attacker as a "terrorist", but gave no more details on his identity. A police spokeswoman said he attacked an Israeli trooper who tried to search him and whose protective vest prevented the knife from causing injury.
The incident took place in a part of Jerusalem's Old City close to a site holy to both Muslims and Jews, where an increasing number of visits by Israelis has stirred Palestinian rancor that has contributed to the past two weeks' surge in violence.