* IAEA says voluntary contributions needed for Iran work
* Western diplomats see no problem in raising required cash
* Iran deal implementation to start on Monday
* IAEA's 35-nation board to meet on issue on Jan. 24 (Adds diplomat comment, detail from report, context)
The U.N. atomic watchdog said on Friday it needed extra money from member states to fund the 6 million euro ($8.2 million)cost of verifying a landmark nuclear agreement between Iran and six world powers.
The International Atomic Energy Agency (IAEA) will play a pivotal role in checking that Iran lives up to its part of the interim deal by curbing its disputed uranium enrichment activity in exchange for some easing of international sanctions that are severely damaging its oil-dependent economy.
The implementation of the six-month accord - meant to buy time for negotiations on a final settlement of the decade-old nuclear dispute - is due to begin on Monday.
Israel, the United States and other western governments have long suspected Iran of using its nuclear energy programme as a cover to develop atomic weapons. Tehran denies this, saying it needs nuclear power to generate electricity.
But last year's election of a relative moderate, Hassan Rouhani, as Iranian president paved the way for a diplomatic thaw with the West, which led to the Geneva accord and eased fears that the dispute could trigger a new Middle East war.
The IAEA's 35-nation board will hold an extraordinary board session on Jan. 24 to discuss the nuclear agency's increased workload as a result of the interim deal between Iran and the United States, France, Germany, Britain, China and Russia.
The IAEA already visits Iranian nuclear sites regularly to make sure there is no diversion of sensitive material for military purposes. It has two to four inspectors on the ground virtually every day of the year.
But its role in Iran, whose nuclear-related sites are spread out across the large country, will expand sharply under the deal hammered out in Geneva nearly two months ago.
A confidential IAEA report to member states, obtained by Reuters, said: "A number of activities additional to those currently being carried out by the Agency in Iran will need to be conducted to confirm Iran's undertakings" under the Nov. 24 Geneva agreement.
They include a significant increase in the frequency of inspections in Iran, access to more sites in the country, a need for more equipment and more analytical work, it said.
"The additional effort will incur increased costs to the Agency," the report, prepared ahead of next week's board meeting, said.
The IAEA's initial estimate of the cost of its monitoring and verification activities in relation to the agreement "is that an additional sum of approximately 6 million euros is needed over the next six months."
Of that amount, "extrabudgetary voluntary contributions of about 5.5 million euros are needed."
The IAEA already devotes about 10 percent of its annual 121 million-euro inspections budget to Iran. The agency's total regular budget for 2014 budget stands at 344 million euros.
Diplomats said they did not believe there would be any difficulty in raising the money required as many member states have already expressed a willingness to help, not only the powers directly involved in negotiations with Iran. The IAEA has 160 member states.
"The money is not going to be an issue," one envoy said.