President Hassan Rouhani said during an event showcasing military hardware broadcast on state-run television: "The strengthening of the capability of the Iranian armed forces… is only for defending the country and we will ask no one's permission to build up the armed forces, and to build missiles and aircraft."
He said Iran has never had "aggressive aims, but peace is not a one-way road and if we decide to be peaceful the other party… may not. So there is a need for vigilance."
Ahead of an upcoming election in the Middle Eastern country in May, the country’s leader had come under fire from opponents who had criticised Mr Rouhani for appeasing the West when he agreed to curb the country’s nuclear programme in exchange for lifting of sanctions.
US President Donald Trump has hit out against the Iranian regime
Mr Trump criticised Iran several times during his presidential campaign, in particular the nuclear dealing stated that he would bring to an end Iran’s missile programme.
When Iran test-fired a new ballistic missile in January, Trump tweeted that it was "playing with fire".
A bill to impose new sanctions on Iran over ballistic missile launches and other non-nuclear activities has been delayed in the US Senate due to concerns about the presidential election.
US President Donald Trump has criticised the regime in Iran
Iran says its missile tests are not covered by the nuclear deal.
The comments come after Director of the CIA, Mike Pompeo, claimed today that President Trump’s recent missile strikes against the Syrian military were a sign the White House was “prepared to engage in activities that are different from what America has been doing these past few years”.
Mr Pompeo also added that states such as Iran should “take note” of US actions.
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Iranian President Hassan Rouhani has threatened to increase the country's missile capabilities
Earlier today it was reported that Russia had mobilised troops and weapons in Vladivostok, just eight miles from the border with North Korea.
Unconfirmed reports indicated that a military convoy of eight surface-to-air missiles, part of Russian Air Defence, were on the move.
The S400 anti-aircraft missiles were moved to Vladivostok, where Vladimir Putin already has a major navy base.
North Korea displayed its latest missiles during a parade
In recent weeks fears have steadily risen that North Korea could become the trigger for a conflict involving the US, China and Russia.
Tensions have been steadily increasing with the regime in North Korea warning the US not to take provocative action, after holding a military parade that appeared to show off new ballistic missiles.
Officials from the secretive state also warned that the country will "hit back with nuclear attacks" if necessary after Mr Trump ordered an armada to the area, including an aircraft carrier, in a show of military muscle.
US President Donald Trump leaves Air Force One
China has pleaded for the US and North Korean to back down from the war-footing.
On Friday, China's Foreign Minister Wang Yi warned that "conflict could break out at any moment".
He said: “We call on all parties to refrain from provoking and threatening each other and not to let the situation get to an irreversible and unmanageable stage."
Iranian President Hassan Rouhani
China has also warned that military conflict over North Korea’s nuclear weapon’s programme could break out “at any moment” as a stand off with the US approached breaking point.
Mr Trump has also said he will take on North Korea without the support of China if necessary.
Russia and Iran threatened to respond to what they described as US “aggression” in a joint statement with other allies, saying that America had crossed a “red line” and added that “we will respond to any aggression.”
The statement, published on media outlet Ilam al Harbi said: "What America waged in an aggression on Syria is a crossing of red lines. From now on we will respond with force to any aggressor or any breach of red lines from whoever it is and America knows our ability to respond well."