John Kerry, the newly-appointed US secretary of state, has described recent developments in Iran's nuclear programme as disturbing and concerning for the United States.
Speaking at his first press conference since being confirmed as secretary of state on Friday, Kerry said Tehran must address the concerns of the international community at talks in Kazakhstan at the end of of this month.
"The international community is ready to respond if Iran comes prepared to talk, real substance and to address concerns that could not be more clear about their nuclear programme. If they don't then they will choose to leave themselves more isolated", he said.
Kerry's comments come amid growing frustration with UN sanctions in the Islamic Republic.
A new Gallup poll has shown that the Iranian people are increasingly baring the economic brunt of the US-backed Western sanctions against their nation.
Of the 1,000 Iranians interviewed by Gallup between December 2012 and January 2013, 56 per cent said sanctions greatly impacted their livelihoods in 2012.
Washington was seen as responsible for the sanctions and their negative impacts by 47 per cent of respondents. Only 10 per cent blamed the Iranian government for the sanctions.
The United States on Wednesday tightened sanctions on Iran to further choke off its oil income and limit Tehran's ability to freely use the money it gets from oil exports.
The global sanctions have also targeted Iran's access to the world banking system, slowing its economy, accelerating inflation and boosting the ranks of the jobless.
Despite the limitations placed on Iran by the sanctions, 63 per cent of those surveyed said they would want Tehran to continue with its nuclear programme.
Only 17 per cent opposed the continued development of the controversial programme that the Iranian government says is for peaceful purposes.
In talks held last May in Baghdad, the so-called P5+1 - the United States, China, Russia, Britain, France and Germany - demanded Iran scale back its uranium enrichment, the part of its programme that causes the most concern because it could provide the key ingredient for a nuclear bomb.