The two Iranian warships that passed through the Suez Canal last month en route to Syria, a move Israel branded "political provocation," will make the return trip on Thursday, an official said.

The Alvand, a frigate, and the supply ship Kharg "will be in Port Said at four in the morning (0200 GMT) to begin passage" towards the Red Sea, the official with the Suez Canal Authority said.

The two ships transited the canal into the Mediterranean on February 22, the first Iranian vessels to do so since the Islamic revolution in 1979.

In response, Israel put its navy on alert. Israel considers Iran, which opposes the Jewish state and supports Hezbollah in Lebanon and the Islamist Hamas group in the Gaza Strip, a serious threat.

Israeli President Shimon Peres called the passage of the two warships through the canal a "political provocation". Tehran described the move as a routine visit.

Analysts said it was an attempt by the Islamic republic to project its clout in the region at a time when anti-government protests sweeping the Arab world from Casablanca to Cairo are shifting the regional balance of power.

Egypt's ruling military council, which has been running the country since president Hosni Mubarak quit on February 11 following massive street protests against his government, approved the ships' passage through the waterway, a vital global trading route.

The Suez Canal Authority said last month that ships of any nationality can pass through "as long as the country is not in a state of war with Egypt."

After the Iranian ships entered the Mediterranean, and steamed past the coast of Israel on their way to Syria, the United States said it was keeping a careful eye on their activities.

"We are watching the situation," said Colonel Dave Lapan, a Pentagon spokesman.

"We have said generally that Iran's actions are not helpful, but we would expect that these Iranian ships would adhere to international law no matter where they operate," Lapan said.

The NATO military alliance also said it was monitoring the Iranian naval presence.

"We follow events in the region and we follow these two Iranian warships with as much interest as we do any other warships in the region," said NATO spokeswoman Oana Lungescu.

"We are monitoring events," she told reporters, refusing to elaborate.

The ships docked on February 24 at the Syrian port of Latakia.

Iran's navy chief, Rear Admiral Habibollah Sayari, said on Monday that Tehran's dispatch of the two warships to the Mediterranean was not aggressive in aim.

"The Iranian strategy is to reinforce its defensive capacities. We do not harbour aggressive intentions against other countries," Sayari said at a news conference in Damascus.

"The visit aims to strengthen old ties between Iran and Syria and to enhance maritime cooperation," the navy chief said, adding the visit had been scheduled before popular uprisings began breaking out across the Arab world.