ISTANBUL — The collapse of another attempt at international outreach to Iran on Saturday has left world powers with few options except to wait — and hope that the bite of sanctions will persuade Tehran to reconsider its refusal to stop activities that could be harnessed to make nuclear weapons.

But their patience could be tested. While the U.S. and others say Iran already is suffering from the wide range of financial and trade sanctions, travel bans and other penalties imposed by the U.N., the U.S., the European Union and others, the Islamic Republic shows no sign of bending.

Uranium enrichment lies at the heart of the dispute, and Iran, which came to the Istanbul talks with six world powers Friday declaring it would not even consider freezing uranium enrichment, left the negotiations Saturday repeating the same mantra. Throughout two days of hectic meetings, it pushed demands it must have known were unacceptable to the six — a lifting of sanctions and acceptance of its enrichment program before any further discussion of its nuclear activities.

“Both these preconditions are not the way to proceed,” EU foreign policy chief Catherine Ashton declared — and added no new talks were planned.

Publicly, the U.S. and other nations concerned that Iran could turn its enrichment program toward making warhead material say that troubles with enrichment have left more time to persuade Iran to heed international concerns than thought just a year ago. Israeli officials now talk of a three-year window — until 2014 — before Iran can make a bomb. That compares with projections of 2011 just three years ago.

Secretary of State Hillary Clinton told NBClast week the new Israeli estimates are “very significant.” The delay, she said, “gives us more of a breathing space to try to work to prevent them from obtaining a nuclear weapon.”