LONDON (Reuters) - Iran said on Tuesday it would boost its military might and also showcased a new fighter jet amid increased tensions with the United States and with regional rivals over conflicts in the Middle East.

Iranian President Hassan Rouhani said the Islamic Republic’s military prowess was what deterred Washington from attacking it, adding that under President Donald Trump the United States was becoming isolated even from its own allies.

“We should make ourselves ready to fight against the military powers who want to take over our territory and our resources,” Rouhani said in a speech broadcast live on state television ahead of Wednesday’s National Defence Industry Day.

“Why does the United States not attack us? Because of our power, because it knows the consequences,” Rouhani added.

Last week, Iran’s Supreme Leader Ayatollah Ali Khamenei also said the United States would avoid any military confrontation with Tehran because of Iranian military might.

Khamenei has rejected Trump’s offer of unconditional talks on a new nuclear deal, prompting Trump to tell Reuters in an interview on Monday: “If they want to meet, that’s fine, and if they don’t want to meet, I couldn’t care less.”

Relations between Washington and Tehran worsened further after Trump in May took the United States out of an international deal that curbed Tehran’s nuclear program in return for an easing of economic sanctions.

Trump branded that 2015 deal as flawed because it did not address Iran’s missile program or involvement in conflicts in Syria and Yemen, and he has reimposed U.S. economic sanctions.

LOSS OF TRUST IN US

Rouhani compared the sanctions on Iran with the U.S. trade war with China and its new tariffs on some imports from Turkey and European countries.

“It’s not only us who do not trust America. Today even Europe and China do not trust them; even American allies like Canada have lost their trust,” he said.

Earlier on Tuesday Rouhani attended a ceremony, broadcast by state TV, that included the fly-past of a new fighter jet called Kowsar, which Iran says is “100-percent indigenously made” and able to carry various weapons and to be used for short aerial support missions.

However, some military experts believe the fighter jet is a carbon copy of an F-5 first produced in the United States in the 1960s.

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“The airframe appears to be an externally unaltered, two-seat F-5 tiger. Whilst it may be domestically manufactured, it’s an entirely foreign airframe,” said Justin Bronk, a research fellow specializing in combat airpower and technology in the Military Sciences team at the Royal United Services Institute.

“It’s a very small lightweight fighter with very small engines which limits the thrust output, a very low internal fuel capacity which limits range, and a very small nose which limits the size and power of radar that you can fit,” he told Reuters.

“All of those constraints are not going to be changed by updating the internal components. While you might put a modern radar, or modern avionics - by Iranian standards - in there, it is still going to be subject to all limitations of the F-5 airframe.”

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Iran’s air force has been limited to perhaps a few dozen strike aircraft using either Russian or aging U.S. models acquired before the 1979 Iranian revolution.

Iran has sent weapons and thousands of soldiers to Syria to help prop up President Bashar al-Assad’s forces, but had to rely on Russia for aerial support due to its own lack of a powerful air force.

The Islamic Republic launched in 2013 what it said was a new, domestically built fighter jet, called Qaher 313, but some experts expressed doubts about the viability of the aircraft at the time.