"The question is not of a visit to the military installations of Parchin. The agency had asked to take samples from the green areas of Parchin because the Americans and others have made accusations," foreign ministry spokesman Hamid Reza Asefi told reporters.

"To demonstrate that we have nothing to hide and that the Iranian nuclear programme is peaceful, we have authorised the agency to take these samples," he added.

Last week the director general of the International Atomic Energy Agency (IAEA), Mohamed ElBaradei, announced that Iran had finally given the green light for his inspectors to probe Parchin, a huge military complex 30 kilometres (19 miles) southeast of Tehran.

The United States has alleged the Iranians may be working on testing high-explosive charges with an inert core of depleted uranium at Parchin as a sort of dry test for how a bomb with fissile material would work.

Environmental sampling involves taking swabs or soil samples to detect the presence of nuclear activity.

The IAEA inspection visit to Parchin is expected to take place within the next few days or weeks, officials have said.

The IAEA has been seeking access to Parchin since July. Tehran has strongly denied carrying out any nuclear-related work at the site, and insists its nuclear drive is merely aimed at generating electricity.

Parchin is an example of a so-called "transparency visit," where the IAEA is going beyond its mandate under the nuclear Non-Proliferation Treatyto check if nuclear materials have been diverted away from peaceful use.

Asefi also responded to a call from ElBaradei that all countries lead by example by committing not to build facilities for uranium enrichment and nuclear reprocessing for five years.

Enriched uranium, depending on its level of purity, can be used to fuel a reactor or as the explosive core of a nuclear weapon -- so the IAEA is keen to limit international fuel cycle use even though it is permitted under the NPT.

"To make a unilateral demand that we suspend for a long period without taking into account the legitimate right of everyone is not logical," Asefi said.

"There must be a balance between such a demand and the right of countries to master peaceful nuclear technology. We have mastered this technology and are not ready to renounce it," he added.

Iran has agreed to freeze uranium enrichment in a deal with the European Union, in return for a package of incentives -- negotiations on which are due to commence this month.

The EU is also seeking "objective guarantees" that Iran will not divert nuclear technology to military purposes, and ideally would like to see Iran abandon its fuel-cycle work altogether.

But Tehran asserts the freeze on enrichment-related activities is only temporary.

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