Hamid Reza Asefi, the foreign ministry spokesman, told a weekly news conference on Sunday: "The NPT is an international commitment and we are committed to that."
Ahmadinejad had told a rally in Tehran on Saturday that Iran might review its commitment to the NPT if the West used the treaty to pressure Tehran to abandon its nuclear programme.
Manouchehr Mottaki, the foreign minister, said Iran had ordered resumption of uranium enrichment activities in its Natanz facility, in defiance of world pressure to give it up. But he also said that Iran would continue to respect the treaty.
"We have informed the IAEA about the order. Iran's peaceful activities will continue based on the NPT," Mottaki told the student news agency ISNA.
Asefi told the news conference that a date had yet to be set for the resumption of activities at Natanz.
"We will act based on our responsibilities within the framework of the NPT and the safeguards agreement"
Hamid Reza Asefi,
foreign ministry spokesman
"... We will act based on our responsibilities within the framework of the NPT and the safeguards agreement," he said.
Western countries have successfully pushed for Iran to be reported to the UN Security Council for failing to convince the world that its atomic programme has exclusively peaceful aims.
Iran says it has no intention of building nuclear arms, as the West suspects, and merely wants to harness nuclear energy to meet growing energy demand.
Asefi called on the West to resume talks over the country's disputed nuclear work.
"The current issue should be resolved through negotiations and the existing regulations," Asefi said.
Some hardline commentators in Iran, who are opposed to Western interference in the country's affairs, have suggested that Iran should pull out of the NPT.
"The best and only solution for Iran is to withdraw from the NPT," said Hussein Shariatmadari, chief editor of the Kayhan newspaper.