* Revolutionary Guards showcase missile test, bunker
* Hardliners say U.S. is still a threat after deal
* Show of strength comes ahead of important elections
* Israel, Gulf Arabs see threat from Iran's missiles
By Sam Wilkin and William Maclean
DUBAI, Nov 4 (Reuters) - As Iran's government promises a new age of prosperity after sanctions, many Iranians are hoping for the best. But the security establishment, with an eye to its political survival, is very publicly preparing for the worst.
In the past few weeks, Iran has begun to implement a historic accord with world powers, voluntarily curbing its nuclear programme in exchange for relief from the sanctions that have cut Tehran off from much of the world.
At the same time, the armed forces have loudly advertised developments to Iran's missile deterrent and other defence capabilities, proclaiming they are still prepared for an attack by the Islamic Republic's enemies.
The increase in martial messaging, which analysts say is aimed both at Iran's enemies abroad and political moderates at home, has alarmed Israel and Gulf Arab countries which are wary of Iran's ambitions in the Middle East.
Supreme Leader Ayatollah Ali Khamenei approved the nuclear deal last month. But he insisted that it did not herald a new era of co-operation with the United States, which he believes is determined to bring about regime change in Tehran.
"America's goals have not changed. If they could destroy the Islamic Republic today, they would not hesitate for a moment," he said on Tuesday.
MEN IN SUNGLASSES
The Islamic Revolutionary Guards Corps (IRGC) and other security hawks, whose narrative of resisting neo-imperialism found a ready audience under sanctions, have happily heeded his warnings.
State television released a video on Oct. 14 showing the head of the IRGC's aerospace division inspecting an underground tunnel complex, purportedly 500 metres (1,600 feet) underground, filled with a variety of missiles on mobile launchers that the presenter said were ready to fire.
With the theme music from the historical epic Gladiator playing in the background, the video showed Brigadier Amir Ali Hajizadeh walking through the underground complex and addressing ranks of uniformed men wearing sunglasses.
The video was released just days after Iran tested a new precision-guided ballistic missile, the Emad, which will be the its first weapon able to accurately strike targets in its arch-enemy Israel.
The armed forces have also announced improvements to Iran's radar and naval capabilities, with an emphasis on domestic production and self-sufficiency, and last week conducted annual civil defence drills.
Michael Elleman, senior fellow at the International Institute for Strategic Studies (IISS), said the tunnels had been in use for a long time, while the Emad missile was likely years away from operational readiness.
That would suggest that the timing of the messages was tied to politics rather than technological advances, he said.
FEARS OF "SEDITION"
Tehran is wary of the United States and Israel, some of whose commentators have called for military attacks on the Iran even after the nuclear deal, and also of Gulf Arab powers who are fighting a proxy war with Iran's allies in Syria and waging a direct conflict against them in Yemen.
Domestically, the security establishment likely has an eye on upcoming elections to parliament and the Assembly of Experts, a clerical body with nominal power over the Supreme Leader, in February next year.
If President Hassan Rouhani's 'nuclear dividend' brings those bodies under the control of his moderate allies, security hawks could see their influence eroded which, in their view, would threaten the Islamic Republic itself.
On Wednesday, hardline demonstrators marched through Tehran carrying missile-shaped balloons and placards warning against U.S. economic influence, on the anniversary of radical students storming the U.S. Embassy after the 1979 Islamic Revolution.
"If the people start thinking our nuclear deal means we can make a deal (with the United States) on other issues, this is a mistake and sedition," IRGC commander Major-General Mohammad Ali Jafari said on Monday.
By invoking "sedition", the word used by hardliners to describe a major reformist uprising that the IRGC put down in 2009, Jafari was hinting that the Guards could once again intervene in domestic politics; and his comments coincided with a crackdown on writers and artists accused of "propaganda against the regime".
BALANCE OF POWER
To Tehran's foes, though, the messaging is a reminder of a potent asymmetric arsenal that includes missiles, irregular forces and allied militias deployed in regional countries, and fast attack boats that could disrupt shipping in the Gulf.
Furthermore, it serves as proof that the IRGC, which controls all of these unconventional assets, has no intention of giving up its regional influence or allowing Iran to align itself with the U.S.-led regional order.
"We don't pore over resolutions; it is our duty to expand our power and nobody can give us orders," IRGC Deputy Commander Hossein Salami said in a televised interview on Oct. 25, responding to allegations that the Emad missile test two weeks earlier may have breached U.N. resolutions.
The IISS noted in its 2015 Military Balance report that Iran's regular forces, while large, are poorly equipped compared to its rivals and would be unlikely to prevail in a conventional conflict waged outside Iran's borders.
The air force, comprised largely of U.S.-made jets obtained before the revolution, is particularly weak compared to Iran's Gulf Arab rivals which have spent billions of dollars on Western fighter aircraft this year alone.
By contrast, Iran's missile arsenal is the strongest in the region and, while conventional missiles alone do not win wars, potential strikes on population centres or oil facilities are a cause for concern in Gulf Arab countries.
Improving the accuracy of missiles, which is Iran's current aim, could expand their potential uses to hitting military bases or attacking crucial civilian infrastructure such as water desalination plants, airports or oil export terminals.
A military source in Qatar said Iran's missile capability was considered the biggest conventional military threat to Gulf Arab countries, as well as U.S. military bases in the region and international shipping routes.
Israel too sees a threat from conventional missile attacks, Defence Minister Moshe Yaalon said last week, without naming Iran explicitly, and said he thought the nuclear deal had delayed but not removed the threat of an Iranian nuclear weapon.
Israel has also expressed concerns that the Hezbollah militia in Lebanon could receive missiles from Iran, which has already supplied the group with smaller unguided rockets, while Saudi Arabia has accused Iran of training the Houthi fighters in Yemen who have seized the country's stock of Scud missiles.
"While these publicity initiatives may look aggressive, the Iranians are always careful to say that the programme is defensive in nature," said Jeremy Binnie, Middle East Editor at IHS Jane's Defence Weekly.
Nevertheless, he added, "now that the nuclear deal is in the bag, maybe it's back to business as usual".
(Additional reporting by Tom Finn in Doha; Editing by Giles Elgood)
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