* Move looks like latest reply to pressure over nuclear work
* Weapons experts believe Iran exaggerates capabilities (Adds comments from Ahmadinejad)
By Yeganeh Torbati
DUBAI, Aug 21 (Reuters) - Iran unveiled upgrades to six weapons on Tuesday, including a more accurate short-range missile and a more powerful naval engine, Iranian media reported, in what seemed to be its latest response to international pressure over its nuclear programme.
The hardware was presented at a ceremony marking Defence Industry Day and attended by President Mahmoud Ahmadinejad and Defence Minister Ahmad Vahidi.
Israel has said it is considering air strikes on Iran's nuclear sites if the Islamic Republic does not resolve Western fears it is developing the means to produce atomic weapons, something the Islamic Republic denies.
Iran says it could hit Israel and U.S. bases in the region if it comes under attack.
It has also threatened to block the Strait of Hormuz, the neck of the Gulf through which 40 percent of the world's sea-borne oil exports pass. Such a move would probably invite a military response from the United States.
Ahmadinejad said on Tuesday that Iran's military advances are purely for defensive purposes and should not be taken as a threat, but said they would dissuade world powers from imposing their will on Iran.
"Defensive advances are meant to defend human integrity, and are not meant to be offensive moves toward others," Ahmadinejad said, according to Mehr news agency.
"I have no doubt that our defensive capabilities can stand up to bullying and put a halt to their plans."
The United States has also not ruled out military action against Iran but says the priority of world powers remains the use of diplomacy and sanctions to rein in its nuclear activity.
Among the upgrades was a fourth generation of the Fateh-110 missile, which boasts a range of about 300 km (180 miles).
Iran said earlier this month that it had successfully test-fired the new model and that it was equipped with a more accurate guidance system.
"This missile is one of the most precise and advanced land-to-land ballistic missiles using solid fuel," Vahidi was quoted as saying by Fars news agency. "In the last decade it has had a significant role in promoting the Islamic Republic of Iran's defence capabilities."
In July, Iran said it had successfully test-fired medium-range missiles capable of hitting Israel, and tested dozens of missiles aimed at simulated air bases.
It also presented a more powerful, 5,000-horsepower sea-borne engine, the Bonyan-4, Fars quoted Vahidi as saying. A previous version had 1,000 horsepower, the Iranian Students' News Agency (ISNA) said.
Military experts have cast doubt on Iran's claims of weapons advances, especially its assertions about its missile programme, saying Tehran often exaggerates its capabilities.
"The Fateh-110 has a crude guidance and control system that operates during the missile's ascent" rather than during final descent, said Michael Elleman, senior fellow for missile defence at the International Institute for Strategic Studies.
"The Fateh-110 appears to lack the subsystems needed to effect terminal steering," he said in an email.
Iran also presented Armita, an "airborne laboratory" to help test aircraft launch systems and oxygen generation and train fighter pilots, Fars reported.
Vahidi said it was named after the daughter of Dariush Rezaeinejad, an Iranian scientist who was shot dead last year.
Iran believes agents working with foreign intelligence services including the American CIA and Israel's Mossad are behind the assassinations of several of its nuclear scientists.
(Reporting by Yeganeh Torbati; Editing by Mark Heinrich)
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