Seventy-four states have already signed an additional protocol with the IAEA although only 35 of them have ratified the legally-binding agreement.
Its main aim is to allow the United Nations' nuclear watchdog to verify a country's declared nuclear activities and ensure the latter is not hiding material it could use to build a nuclear bomb.
The protocol obliges countries to provide the IAEA with much more precise information about their nuclear activities than is required under the NPT. And it authorises the IAEA to carry out more intrusive inspections of nuclear facilities.
Under the agreement, states commit to giving IAEA inspectors information about, and short-notice access to, all parts of their nuclear fuel cycle, including uranium mines, fuel production and enrichment plants, and nuclear waste sites. They must also offer access to any other location where nuclear material is or may be present.
The IAEA may give as little as two hours' notice before it visits a site to check for evidence of undeclared nuclear material or resolve inconsistencies in the information the government has provided about its nuclear activities.
Once at a site the IAEA is authorised to inspect it, examine records, take samples, use radiation detection equipment and impose seals or other tamper-indicating devices. The agency may also make use of established satellite surveillance systems.
States which sign the protocol have one month, from the time of the request, to issue nuclear inspectors with multiple entry visas valid for at least one year.
The additional protocol cannot work miracles but it does improve the IAEA's chances of discovering the true extent of a country's nuclear activities.
"There's never a 100-percent guarantee when it comes to verification but the additional protocol raises the level of security," an IAEA official told AFP recently.