* Major powers, Iran resume talks to resolve technical issues
* Iran hardliners warn over further U.S. sanctions
* Official says Iran building new centrifuges (Adds Iran nuclear chief’s comments, paragraphs 4, 16-19)
By Justyna Pawlak and Parisa Hafezi
BRUSSELS/ANKARA, Dec 27 (Reuters) - Experts from Iran and six world powers will resume talks on Monday on how to roll out last month’s landmark nuclear deal in Geneva, hoping to resolve numerous technical issues before the accord can take effect.
A spokeswoman for European Union foreign policy chief Catherine Ashton, who oversees diplomacy with Iran on behalf of the United States, Russia, China, France, Britain and Germany, said talks were scheduled to last one day for now.
Two rounds of negotiations have been held so far since Iran agreed on Nov. 24 to curb its most sensitive nuclear work in return for relief from some economic sanctions that are damaging its oil-dependent economy.
In comments that highlight the challenges facing negotiators, Iran’s nuclear chief said on Friday Tehran was pressing on with tests of more efficient uranium enrichment technology. His comments appeared aimed at soothing the anger of Iranian hardliners over possible new U.S. sanctions on Iran.
The nuclear experts have to work out when the deal will be implemented, triggering the loosening of economic restrictions by the EU and the United States.
A key sticking point appears to be what information Western governments will receive in advance to verify that Iran is meeting its end of the deal before they lift some sanctions.
Other outstanding issues address how exactly sanctions will be eased and practical details of Iranian concessions.
Some diplomats from the six nations have said they hoped the deal could be put fully in place by the second half of January.
The talks resume at a sensitive time. Iranian hardliners, irked by the foreign policy shift since moderate President Hasan Rouhani was elected in June, oppose the Geneva deal and call it “a surrender to America’s pressure” by the government.
A group of 100 hardline Iranian lawmakers are seeking to oblige the government to increase uranium enrichment to 60 percent, a level that can produce bomb-grade material if enriched further, if new U.S. sanctions are imposed on Tehran.
It is not clear if the bill will be debated in Iran’s 290-seat parliament as the country’s most powerful authority, Supreme Leader Ayatollah Ali Khamenei, has repeatedly backed the Geneva talks. If approved, the bill would have to be ratified by a constitutional watchdog body to become law.
Iranian lawmakers said their bill was a response to “America’s hostile measures”, referring to legislation introduced by 26 U.S. senators last week to impose new sanctions on Iran if the Islamic Republic breaks the Geneva deal.
A hardline Iranian MP said the process could be derailed if the U.S. lawmakers imposed the tougher curbs despite the Obama administration’s opposition.
“Ratification of such a bill could put an end to nuclear negotiations and Tehran may opt not to continue negotiations in the wake of such sanctions,” said the deputy head of the Iranian parliament’s National Security and Foreign Policy Committee, Mansour Haqhiqhatpour, Press TV reported.
The proposed U.S. legislation would require reductions in Iran’s petroleum production and apply new penalties to Iran’s engineering, mining and construction industries.
To calm the hardliners, nuclear chief Ali Akbar Salehi said Tehran was testing more efficient uranium enrichment technology by building a new generation of centrifuges - machines that spin at supersonic speed to increase the ratio of the fissile isotope that could enable it to refine uranium much faster.
Although the development does not appear to contravene the Geneva accord, it may worry the major powers who are trying to curb the Islamic state’s nuclear programme.
“The new generation of centrifuges is under development. However, tests should be completed before mass production of the centrifuges,” Press TV quoted Salehi as saying.
Salehi also said Iran had a total of 19,000 centrifuges, without elaborating on how many were operational.
A spokesman for Iran’s Atomic Energy Organisation announced on Dec. 7 that initial testing on a new generation of more sophisticated centrifuges had been completed.
Iran rejects Western fears that its nuclear work has any military intentions and says it needs nuclear power for electricity generation and medical research.
The Nov. 24 deal is meant to give the six powers time to negotiate a final settlement with Iran that will put an end to the decade-old standoff and ease worries over a new war in the Middle East. (Editing by Toby Chopra and Gareth Jones)