US rejects Iran nuclear proposals
Iran's Foreign Minister Manouchehr Mottaki, right, submitted the proposals
The US says it is unhappy with the package of proposals submitted by Iran on Wednesday aimed at breaking the deadlock over its nuclear ambitions.
Philip Crowley of the US State Department told the BBC the measures do not address the status of Iran's nuclear programme.
The US wants Iran to suspend its uranium enrichment programme which its says could be used for nuclear weapons.
Iran says its nuclear programme is for civilian use.
"Our concern is that the response itself did not really address what is the core issue of the international community and the core concern, which is Iran's nuclear ambitions," Mr Crowley told the BBC's World Today programme.
Earlier, Mojtaba Samareh, a close aide to the Iranian President, told the Washington Post newspaper his country would not give up its nuclear programme but was willing to work with the international community to eliminate nuclear weapons.
Based on a brief review of the Iranian papers my impression is there is something there to use
Sergei LavrovRussian Foreign Minister
Mr Crowley said Iran had to prove it was ready to live up to commitments it had made.
"One of the questions going forward will be to test the Iranian interest in actual engagement, either with the United States or the international community and obviously a core concern is in fact its nuclear programme," he said.
Iran hopes the proposals - to be reviewed by the five permanent UN Security Council members and Germany on Friday - will head off new international sanctions.
Russia has given a more positive response than the US to Iran's latest proposals.
Iran insists its rocket building programme is for satellites
Russian Foreign Minister Sergei Lavrov said they contained something to work with.
"Based on a brief review of the Iranian papers my impression is there is something there to use," Mr Lavrov said in Moscow.
"The most important thing is (that) Iran is ready for a comprehensive discussion of the situation, what positive role it can play in Iraq, Afghanistan and the region."
The BBC's Bridget Kendall, in Moscow, said his comments left little doubt that Russian and Western approaches to Iran continue to diverge.
Finding common ground for a united response to the latest Iranian proposals may prove tricky, she adds.
US President Barack Obama warned Tehran earlier this year that Washington wanted to see a positive response to its friendlier overtures by the end of September.
If not, Mr Obama said the US was prepared to press for new sanctions against Iran.
But Mr Lavrov added that he did not think the UN Security Council would support oil sanctions against Iran.
"Some of the sanctions under discussion, including oil and oil products, are not a mechanism to force Iran to co-operate, they are a step to a full-blown blockade and I do not think they would be supported at the UN Security Council," he said.
Details of Iran's latest proposals have not been revealed.
On Wednesday, the US envoy to the International Atomic Energy Agency (IAEA), Glyn Davies, said Iran could already have enough low-enriched uranium to produce a bomb, if it was further enriched.