Iran's UN ambassador says Tehran will not only sign but observe a key international measure against nuclear proliferation even before its ratification by the Iranian parliament.
Tehran had previously agreed in principle to sign the document, as well as to suspend enrichment of nuclear fuel, in what was seen as a major step forward in its months-long standoff with the International Atomic Energy Agency (IAEA) over its nuclear ambitions.
But it had not previously publicly said it would meet its obligations under the pact even before its ratification.
It has still not said, however, exactly when it would sign the measure, which is known as the additional protocol to the Non-Proliferation Treaty and would allow snap inspections by IAEA experts of its nuclear sites.
Ambassador Javad Zarif announced the step to the 191-nation UN General Assembly during discussion of the annual report of the IAEA, which is the UN nuclear watchdog agency.
"As further confidence-building measures, for the present, Iran has voluntarily decided to suspend uranium enrichment activities, sign the additional protocol and continue to cooperate with the IAEA in accordance with the protocol, pending its ratification, which will have to be done by the Iranian parliament," Zarif said.
Mr Zarif insisted Iran had an "inalienable right" to pursue nuclear technology for peaceful purposes, but said nuclear arms "have no place in Iran's defence doctrine."
In Tehran, Iran's Supreme Leader Ayatollah Ali Khamenei warned his country would end co-operation with the IAEA if further demands undermined Iran's national interests.