"We will suspend our activities for as long as we deem necessary, and we will resume our activities if we judge it necessary," said Hassan Rowhani, the secretary of Iran's powerful Supreme Council of National Security.
"This could be for one day, one year or longer. The decision is ours," he told reporters.
Iran on Tuesday yielded to international demands for it to prove it is not developing nuclear weapons, promising Britain, France and Germany it would give "full cooperation" to the UN's nuclear watchdog and bow to an intrusive inspections regime.
It also agreed to suspend enrichment, another demand made by the International Atomic Energy Agency (IAEA).
When asked when Iran would sign the additional protocol to the nuclear Non-Proliferation Treaty (NPT) -- the text that gives IAEA inspectors more clout -- Rowhani said Iran would likely officially write to the IAEA before its next board of governors meeting on November 20 signalling its intention to sign.
He declined to give any further details.