United Nations inspectors visited a uranium enrichment plant in Brazil Tuesday, seeking to resolve an impasse over the country's refusal to permit visual inspection of its uranium centrifuges.

Three International Atomic Energy Agency (search) inspectors from South Africa, France and the United States arrived Tuesday morning at the plant in Resende (search), some 60 miles northwest of Rio de Janeiro, said Mines and Energy spokesman Gustavo Cruz da Souza.

Brazilian officials do not want to allow full visual inspection of the centrifuges, citing fears the plant's advanced technology could be stolen by other countries if outsiders were allowed to view it.

Brazil claims it has developed new electromagnetic technology that reduces friction in the centrifuges and makes them 30 percent more efficient than those used in other countries.

Some analysts have suggested, however, that Brazil will not allow inspectors full access because it purchased the technology on the nuclear black market — a charge the government denies.

Brazilian officials planned to lower some of the panels concealing the centrifuges but would not reveal them entirely to the inspectors, Souza said. Brazil wants the inspections limited to examinations of the tubes and valves leading to the centrifuges.

The inspectors were to spend the entire day at the plant and would not talk to the press, Souza said.

On Monday, Odair Dias Goncalves (search), president of Brazil's National Nuclear Energy Commission, said the IAEA was no longer insisting on "total and unrestricted access" to the centrifuges.

The IAEA has never demanded unrestricted and total access in Brazil, a diplomat close to the agency said.

"We're insisting on visual access that would be sufficient to rule out any diversion of nuclear material from that plant," IAEA spokeswoman Melissa Fleming said.

She added, the agency "needs physical access to the parts that would be crucial in determining that all nuclear material is accounted for and none is leaving that building."

On Wednesday, the inspectors are expected to decide whether Brazil's proposed inspection regime is acceptable.

If the inspectors approve Brazil's proposal, another team would be sent to approve the plant's design and Brazil could begin enriching uranium.

Uranium enriched to low levels is used for fuel to generate power. More highly enriched, weapons-grade uranium can be used in nuclear warheads. Brazil denies it is building such arms.

But Brazil's refusal to deny the IAEA full access has prompted fears that countries like North Korea and Iran could point to the Brazil's example to justify their own lack of compliance with the agency.