"A suspension does not make any sense to us, because we do not think an atomic bomb can come out of a 164 centrifuge cascade," Ali Larijani was quoted as saying by the ISNA news agency.

Iran has installed 164 centrifuges at a pilot plant for the sensitive process of uranium enrichment -- which on a large scale can be extended to making nuclear weapons.

Iran argues it is so far only carrying out "research" work, and only wants to eventually make civilian reactor fuel. On Friday a UN Security Council deadline for the work to stop expired without Iranian compliance.

Iran is now facing a Western push for tougher Council action, and Larijani repeated Iran's warning that increased international pressure could force it to halt UN inspections and even quit the Non-Proliferation Treaty.

"We see no reason to quit the NPT. We won't do so if they do not force us," Larijani said.

Iran says it wants to enrich uranium only to make reactor fuel to generate electricity, as is authorised by the NPT. But Western powers want a suspension of the work while suspicions over Iran's nuclear programme remain.