White House spokesman: "It doesn't really change anything that we've said, that Iran should fully suspend its enrichment and reprocessing activity in compliance with the international community, which has spoken at both the IAEA and in the UN Security Council."   

EU diplomat accredited to IAEA, asking not to be named: "The Security Council called on Iran to resume full and sustained suspension of all enrichment and reprocessing activities including research and development. To have 164 centrifuges up and running would not [reflect] that call. If Iran doesn't comply, the Security Council will revisit the issue. There can be no mistaking the message from the council."

David Albright, former UN arms inspector and nuclear specialist: "In terms of timing, this was entirely predictable. They seem to have reached the point of learning how to run a cascade and that's significant. The key question is whether Iran is now demonstrating more knowledge than it has reported to the IAEA in the past. But the cascade is a tricky thing to operate and you need experience and time to ensure it's not going to crash. It's like a racing car engine. You build a new one and turn it on but that doesn't mean you immediately install it in the car and speed away; you have to run this engine for quite a while to see if it's reliable and no problems crop up."

Diplomat familiar with IAEA work in Iran: "This is no particular surprise. The Iranians were clearly working on this since announcing in January they would end the suspension of enrichment work. But this marks a fork in the road. It represents a technological achievement. It probably strengthens their bargaining position [with the West] as well. The caveat to all of this is to actually authenticate what the Iranian claims are. IAEA inspectors are there now, they would have visited Natanz and Isfahan. What they find out will be in ElBaradei's report destined for the Security Council at the end of April. A key question is whether Iran made these centrifuges or did they come from Pakistan? Fact is, they have a long way to go to reach industrial-scale enrichment. They have a hole in the ground for 50,000 cascades but just 164 centrifuges are running now."   

Robert Einhorn, former US non-proliferation official: "It's hard to know what we make of it because if they really believe they've reached a milestone - which is confidence that they can operate this 164 machine cascade - then that is much sooner than we anticipated. Usually when you run a test cascade like that you want to run it for quite some time to see how it's performing. It's hard to evaluate the operation of this experimental facility on the basis of a few weeks. It can't be more than a week or so that they have had gas circulating in that cascade. It's probably a kind of premature declaration of success and perhaps done for political reasons."