TEHRAN - A team led by the U.N. nuclear watchdog's second-in-command held talks in Tehran on Tuesday with Iranian officials to try to clear up questions about the country's disputed atomic programme.

Iran agreed with the International Atomic Energy Agency (IAEA) in August to explain the scope of its nuclear work, which the West fears is a cover for building an atomic bomb. Iran denies the charge saying its atomic work is peaceful.

As part of the deal, an Iranian team met IAEA officials in September to answer outstanding questions over centrifuges used for uranium enrichment, a process that can make fuel for nuclear power plants or, if Iran wanted, material for nuclear warheads.

State television said the talks began between Olli Heinonen, IAEA deputy director-general, and Iran's deputy nuclear negotiator, Javad Vaeedi. IRNA news agency said the IAEA team, which arrived early on Tuesday, would stay two or three days.

Talks would cover P-1 and P-2 centrifuges, IRNA reported. Iran uses a 1970s vintage of centrifuge, called P-1s, prone to breakdown if spun at high speed for long periods. It is researching an advanced P-2 model at sites off limits to IAEA inspectors.

"The process is on track," a senior Vienna diplomat familiar with IAEA-Iran contacts said, adding that two sides were meeting earlier than the previous plan of mid-October. "I would treat the earlier date for this meeting generally as a positive step."

The deal with the IAEA allows Iran to settle questions one by one over a timeline the agency says would run to December.

The U.N. Security Council has imposed two sets of limited sanctions on Tehran for its refusal to halt enrichment, the part of Iran's programme that most worries the West.

Major powers have agreed to delay further U.N. sanctions until November, to see whether the pact between Iran and the IAEA yields results, and to await a report by European Union negotiator Javier Solana on talks with Iran.

The U.N. Security Council and Germany are negotiating on a third resolution against Tehran. France and Germany have also signalled that Europe could punish Iran for pressing ahead with its nuclear work before further U.N. sanctions.