* UN agency's talks with Iran separate from big power diplomacy
* Watchdog wants to resume inquiry into alleged bomb research
* Iran says nuclear programme entirely peaceful
The U.N. nuclear watchdog said on Tuesday a planned meeting with Iran next week to discuss steps meant to ease concerns over its nuclear programme has been pushed back to Feb. 8 at Tehran's request.
The International Atomic Energy Agency did not say why Tehran asked for a delay. But the original date, Jan. 21, is just a day after Iran and big powers are to start implementing an interim deal on curbing Iranian nuclear activity, suggesting a busy agenda in coming days may have led to the postponement.
The IAEA has been tasked with checking that Iran carries out its end of the six-month preliminary accord, so the U.N. agency is also facing an extra workload.
The IAEA-Iran negotiations that have now been postponed are separate from - albeit still closely aligned with - broader, high-level diplomacy between Tehran and six world powers over Iran's nuclear programme.
In November, Iran and the IAEA struck a cooperation pact, including six initial steps to be taken by Tehran over the following three months, entailing access to two nuclear-related facilities and the provision of information.
They said after a review meeting last month they would meet again in Tehran on Jan. 21 to discuss the next steps under the framework agreement.
Western diplomats say those measures may be increasingly difficult to negotiate, as the IAEA has made clear it wants to resume a long-blocked investigation into what it calls the possible military dimensions to Iran's nuclear programme.
IAEA spokeswoman Gill Tudor confirmed that the date of the meeting had been changed and that "this was at Iran's request". There was no immediate comment from Iran's IAEA mission.
The IAEA wants Iran to address allegations that it has researched how to develop a nuclear bomb, a charge Iran denies.
The Islamic Republic says its nuclear energy programme is wholly peaceful. But it concealed sensitive activity from IAEA inspectors in the past, stoking suspicions abroad.
PACT BETWEEN IRAN, BIG POWERS TO TAKE EFFECT JAN. 20
Iran and the six powers - the United States, France, Germany, Britain, China and Russia - said on Sunday the implementation of their Nov. 24 preliminary accord would begin on Monday. Iran agreed to scale back some activity of potential use in producing a nuclear bomb, in return for some easing of economic sanctions.
The IAEA will play a pivotal role in verifying that Iran fulfils its part of the bargain. A group of IAEA inspectors will travel to Iran on Saturday "to implement the first step" of the accord, Iran's Atomic Energy Organisation said.
The landmark agreement, nailed down after a decade-long standoff, appeared to stem a slide towards another Middle East war over Tehran's nuclear ambitions, although diplomats warn that mistrust remains so deep it will not be easy to implement.
The IAEA's 35-nation Board of Governors is to hold an extraordinary meeting on Jan. 24 to discuss the extra work burden facing inspectors in monitoring the pact between Iran and the six states, diplomats said on Tuesday.
The IAEA has long inspected Iranian nuclear sites regularly to ensure no diversions of material for military purposes.
It will now both increase the frequency of such visits and examine additional sites including plants where Iran manufactures equipment for refining uranium.
Enriched uranium can fuel nuclear power plants or, if processed much further, nuclear bombs.
For its increased workload, the IAEA likely needs to send more inspectors to Iran. It has tentatively identified extra costs of some 5 million euros ($6.83 million), to be funded in part by voluntary member state contributions, diplomats said.