Iran says its uranium enrichment work is "irreversible" and it will not abandon its nuclear program.
The latest salvo in the international standoff comes just days before a U.N. deadline for Iran to stop enrichment.
Iran's foreign ministry spokesman, Hamid Reza Asefi, says Iran has no intention of stopping its nuclear enrichment program, and is prepared to face the consequences.
He says, "We are determined to defend our rights. Nuclear research will continue, and suspension of nuclear activities is not on our agenda. The issue is irreversible."
The U.N. Security Council has given Iran until Friday to freeze its uranium-enrichment program.
The U.N. nuclear watchdog agency is supposed to report on Iran's compliance on April 28th.
Iran announced earlier this month that it has successfully enriched uranium to the level needed for nuclear power stations. Western nations believe Iran may be trying to build a nuclear bomb, but Iran says its nuclear ambitions are peaceful.
Asefi told reporters in Tehran that Iran will not respond to what it sees as threats.
He says, " Iran will not renounce its rights. We are ready, and we have made plans for all possible eventualities."
The United States says it wants a diplomatic solution to the crisis, but has also refused to rule out the use of military force against Iran.
Other nations involved in the standoff, including Russia, China and France, oppose a military solution, which they say could have disastrous consequences in the region and the world.
The Iranian foreign ministry spokesman said Tehran is still discussing a Russian plan for joint uranium enrichment on Russian soil.
Iranian and Russian officials last month announced what they called a basic agreement on the plan, but no details have emerged.
Iranian officials say they are currently using a cascade of 164 gas centrifuges, but plan to expand that to three-thousand centrifuges by the end of the year.
Last week, President Mahmoud Ahmadinejad said Iranian scientists are experimenting with a more advanced type of centrifuge known as P-2, which could enrich uranium faster.
Asefi said the P-2 machines have not been used yet.