"We are sending a consignment of 1,000 tons on a ship to Gaza the beginning of next week," Red Crescent secretary general Ahmad Moussavi was quoted as saying on the organization's website.
"There is the possibility of our ship being blocked just as the Libyan ship was blocked," he added referring to a vessel intercepted by Israel a month ago.
Libya protested to the UN Security Council over Israel's interception of the cargo ship, which had sought to take 3,000 tons of humanitarian aid to Gaza.
Israel said that because Libya does not recognize it, the interception was justified on grounds of national security.
"Unfortunately so far the Egyptian government had not allowed us to send the relief items to them by air," Moussavi said, referring to Gaza's southern neighbor
The official did not disclose the nationality of the ship, but said the cargo will include 500 tons of wheat, 200 tons of sugar, 200 tons of rice, 50 tons of cooking oil and 50 tons of medical supplies.
The Israeli embargo was imposed after the Islamist Hamas seized power in Gaza in June 2007. The blockade has been tightened since the start of November in retaliation for rocket fire on southern Israel.
Tehran is a staunch supporter of Hamas and has rejected all allegations that it is supplying arms to the movement, saying it only provides moral backing.
Iranian President Mahmoud Ahmadinejad has repeatedly called for Israel to be wiped off the map and even called the Jewish Holocaust a "myth."