Iran's President Mahmoud Ahmadinejad has warned his country's military would deal with any attack by "cutting the hand of the aggressor".
Mr Ahmadinejad says Iran's nuclear intensions are peaceful
Mr Ahmadinejad was speaking after US media reports last week said the US might take military action to try to stop Iran developing nuclear weapons.
The five permanent members of the UN Security Council and Germany are to discuss the nuclear row in Moscow.
Unease about the stand-off has helped push oil prices to record highs.
Prices hit $70.86 a barrel on Tuesday, and analysts said prices would continue to rise as long as the dispute appeared to escalate.
'Preparing for the worst'
In a speech on Tuesday, Mr Ahmadinejad said he wanted peace and security in the region but added the army should be equipped with the latest technology to deter any aggression.
NUCLEAR FUEL CYCLE
Mined uranium ore is purified and reconstituted into solid form known as yellowcake
Yellowcake is chemically processed and converted into a gas by heating it to above 64C (147F)
Gas is fed through centrifuges, where its isotopes separate and process is repeated until uranium is enriched
Low-level enriched uranium is used for nuclear fuel
Highly enriched uranium can be used in nuclear weapons
"Today, you are among the world's most powerful armies because you rely on God," he told military officers at a parade to commemorate Army Day.
"Iran has created a powerful army that can powerfully defend the political borders and the integrity of the Iranian nation and cut the hand of any aggressor and place the sign of disgrace on their forehead."
The BBC's Frances Harrison in Tehran says the message of the parade and the increasingly frequent military manoeuvres is that Iran is preparing for the worst, while still hoping the world will accept it as a nuclear power.
Speaking ahead of the Moscow meeting, Russian foreign ministry spokesman Andrej Krivtsov said Russia would reaffirm its view that there was no alternative to a negotiated strategy.
The US has said the UN Security Council would have to look at options to compel Iran to "obey the international system" after Iran announced it had succeeded in enriching uranium.
Asked on Tuesday whether the US was prepared to use force, President George W Bush said all options were on the table - but the US wanted to "solve this issue diplomatically and we're working hard to do so".
"The best way to do so is for there to be a united effort with countries who recognise the danger of Iran having a nuclear weapon," Mr Bush said.
Tehran has insisted it will continue its nuclear programme as it is purely for peaceful, energy purposes.
Western nations suspect Iran of wanting to develop a nuclear weapon. Tehran says it has succeeded in enriching uranium, but insists its programme is purely peaceful.