Key European states on Tuesday circulated their own draft resolution imposing nuclear and missile-related sanctions on Iran after failing to reach agreement with Washington, US and European officials said.
A senior US official predicted the dispute would ultimately be resolved, but it was unclear when that might happen.
A unified front among Britain, France, Germany -- lead negotiators with Iran -- and the US has been key to international efforts to curb Tehran's nuclear program, which the West says is aimed at making weapons and Iran says is for energy production.
However, the allies split over some issues, including a US demand that Russia be forced to halt work at Iran's Bushehr nuclear power plant, US officials and European diplomats said.
"The Europeans have told the US that we're going to circulate the text among the permanent five members of the UN Security Council and planned to do it today," one diplomat said.
But a senior US official said: "On Bushehr, I think they'll solve it" by allowing some work on the project -- worth an estimated US$800 million to Russia -- to proceed.
Meanwhile, Iran's student news agency reported yesterday that the country has installed a second cascade for uranium enrichment and will start injecting UF6 uranium gas into it this week.
"Iran's second cascade has been installed two weeks ago and the injection of gas into it will be done this week," the agency quoted an informed source as saying. "Soon after injection of the gas, we will obtain the product of the second centrifuge cascade."