Iran has warned it will change its nuclear policies if states urging it to suspend nuclear enrichment carry out threats against the country.
Iran denies claims it is trying to make atomic bombs
The permanent UN Security Council members have been meeting to try to agree a resolution that could include sanctions against Iran.
The chief Iranian nuclear negotiator, Ali Larijani, said Iran still believed in a negotiated settlement.
He did not spell out how Iranian nuclear policy might change.
But the BBC correspondent in Teheran says it could mean suspending international inspections of nuclear sites or its membership of the nuclear non-proliferation treaty.
Mr Larijani also resisted pressure to respond formally to a package of incentives designed to get Iran to suspend uranium enrichment, saying it needed until late August to formulate its response.