One of al Qaeda's top leaders, who is hiding in Iran, is suspected of helping to organize the bombings in Saudi Arabia last week, and terrorism experts believe he may be trying to unleash as many strikes as possible in a short period of time to prove al Qaeda is still viable, U.S. officials said yesterday. Saif Adel, an Egyptian who intelligence officials believe has assumed the role of the network's military commander, is believed to have given the go-ahead for the Riyadh bombings that killed 34, two senior administration officials said.