The United States today rejected Iranian calls for more time to study an offer of incentives to curb its nuclear fuel programme, insisting Tehran must respond by a G8 deadline next week.
The Group of Eight industrialised nations told Iran yesterday they wanted a "clear and substantive response" on July 5th to an offer of incentives to stop enriching uranium.
But Iranian officials said more time was needed.
A Western diplomatic source said the Islamic Republic was unlikely to give a firm answer but that if one did not arrive by July 12th, when foreign ministers next meet, UN Security Council action would loom.
US Undersecretary of State Nicholas Burns insisted the offer was "very straightforward" and Iran's chief negotiator Ali Larijani should respond as requested at a July 5th meeting with European Union foreign policy chief Javier Solana.
"It is now high time, frankly, that we had a response from the Iranian government ... We always said this was a process of weeks not months," Mr Burns told a news briefing.
But Russian Defence Minister Sergei Ivanov signalled that a definitive Iranian reply was not expected on July 5th.
"At the meeting they will discuss the [offer] and discuss when Iran is ready to distinctively and unequivocally formulate its reply ...," Mr Ivanov told reporters in Moscow.
Mr Larijani's scheduled session with Mr Solana will come one month after the EU leader delivered the package of trade, technology and other incentives to Tehran for consideration.