US President Barack Obama, who is seeking tougher UN sanctions against Tehran, acknowledged that such measures would not necessarily work, but said sustained world pressure could over time prompt Iran to revise its nuclear calculations.

During a ceremony marking Iran’s National Day of Nuclear Technology, President Mahmoud Ahmadinejad pulled back a white curtain to reveal one of the tall, cylindrical machines to a crowd of assembled dignitaries. The display capped months of announcements about the development of the new machines.

Ahmadinejad, in his speech, called the nuclear arms reduction treaty that Obama signed with Russia this week “a masquerade” hiding his true intentions.

“We consider nuclear weapons to be against humanity,” he said.

“Iran’s nuclear path is irreversible. The Iranian nation has reached a new point where no power can deter it from moving full speed ahead to reach peaceful nuclear energy.”

The head of Iran’s Atomic Energy Organization, Ali Akbar Salehi, said the latest “third generation” centrifuges had a separation power of 10, six times that of the first generation.

The centrifuges Iran uses now are adapted from a 1970s design and have been prone to breakdowns. Tehran is known to have been testing new models for years. It was not immediately clear when the new machines would be introduced into full-scale enrichment, something analysts say would be a significant step.

“This is not unexpected and given what Obama is doing, I think they are really trying to show that they are getting past the sanctions,” said David Albright, director of the Institute for Science and International Security in Washington.

“They have been buying a lot for their centrifuge program in the past couple of years, or trying to, and have been thwarted many times. They’ve been working on these third generation centrifuges since the early 2000s,” he said.

“The real issue is, are they able to build these in the thousands or ... in the 10s, and when are they going to be installed? The other question is, do they work well?” Western analysts say Iran has in the past exaggerated progress to bolster domestic pride about its nuclear program and to enhance its bargaining position with major powers.

Western countries are seeking the support of Russia and China for a fourth round of UN sanctions against Tehran.

Britain voiced concern about Iran’s latest show of enrichment devices.

“The use of this kind of technology is of course prohibited by five UN Security Council Resolutions which require Iran to suspend its enrichment program and come clean about its nuclear intentions,” a Foreign Office spokesman said.