JERUSALEM (Reuters) - An Israeli submarine sailed the Suez Canal to the Red Sea as part of a naval drill last month, defense sources said on Friday, describing the unusual maneuver as a show of strategic reach in the face of Iran.

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Israel long kept its three Dolphin-class submarines, which are widely assumed to carry nuclear missiles, away from Suez so as not to expose them to the gaze of Egyptian harbormasters.

It was unclear when last month the vessel left the Mediterranean. One source said the voyage was planned for months and so was not related to unrest after the June 12 re-election of President Mahmoud Ahmadinejad, whom the Israelis see as promoting the pursuit of nuclear weapons to threaten them.

Sailing to the Gulf without using Suez would oblige the diesel-fueled Israeli submarines, normally based in the Mediterranean, to circumnavigate Africa -- a weeks-long voyage. That would have limited use in signaling Israel’s readiness to retaliate should it ever come under an Iranian nuclear attack.

Shorter-term, the submarines’ conventional missiles could also be deployed in any Israeli strikes on Iran’s atomic sites, which Tehran insists have only civilian energy purposes.

A defense source said the Israeli navy held an exercise off Eilat last month and that a Dolphin took part, having traveled to the Red Sea port though Suez. Israel has a naval base at Eilat, a 10-km (6-mile) strip of coast between Egypt and Jordan, but officials say it has no submarine dock there.

“This was definitely a departure from policy,” said the source, who declined to give further details on the drill or say whether the Dolphin had undergone Egyptian inspections in the canal, through which the submarine sailed unsubmerged.

A military spokeswoman had no immediate comment on the voyage, first reported on Friday by the Jerusalem Post.

EGYPTIAN POSITION

Egyptian officials at Suez said they would neither confirm nor deny reports regarding military movements. One official said that if there was such a passage by Israelis in the canal, it would not be problematic as Egypt and Israel are not at war.

Egypt is one of only two Arab states to have signed a peace treaty with Israel, but relations remain cool. However, Arab states that are allies of the United States appear to share some of Israel’s concerns about non-Arab Iran’s nuclear program.

Israel is assumed to have the Middle East’s only atomic arsenal, but does not discuss this under an “ambiguity” policy billed as deterring its enemies while avoiding provocations.

Another Israeli defense source with extensive naval experience said the drill “showed that we can far more easily access the Indian Ocean, and the Gulf, than before.”

But the source added: “If indeed our subs are capable of doing to Iran what they are believed to be capable of doing, then surely this is a capability that can be put into action from the Mediterranean?”

Each German-made Dolphin has 10 torpedo tubes, four of them widened at Israel’s request -- to accommodate, some independent analysts believe, nuclear-tipped cruise missiles. But there have been questions about whether these would have the 1,500-km (1,000-mile) range needed to hit Iran from the Mediterranean.

Israel plans to acquire two more Dolphins early next decade. Naval analysts say this could allow it to set up a rotation whereby some of the submarines patrol distant shores while others secure the Israeli coast or dock to undergo maintenance.