The U.N. nuclear watchdog chief said on Thursday Iran was clarifying atomic development efforts on schedule, countering Western doubts, but Tehran must step up cooperation to resolve remaining questions this year.

Mohamed ElBaradei summarized findings of an International Atomic Energy Agency report on Iran at a debate of the IAEA's governing board, where differences simmered over whether Iran's improved transparency is cause for hope or further skepticism.

The West fears Iran is secretly trying to build atom bombs. Iran says it only wants electricity from uranium enrichment.

Western states on the 35-nation board were expected to dwell on Iran's defiant campaign to enrich uranium despite agreeing to a plan for transparency. Developing nations were likely to highlight Iranian steps towards openness and warn against rising Western pressure they feel could lead to dangerous conflict.

ElBaradei, believed to be concerned by U.S.-led criticism of the transparency plan's limitations and resolve to isolate Iran with harsher sanctions, said the plan was on track -- after some Western powers suggested Iran was dragging its heels.

It is proceeding according to schedule ... There has been good progress, he said, in getting Iran to own up after years of stonewalling about secret 1980s and '90s efforts to acquire centrifuge enrichment technology from nuclear smugglers.

Our progress over the past two months has been made possible by an increased level of Iranian cooperation.

However I would urge Iran to be more proactive in providing information and accelerating the pace of cooperation so the agency will be able to clarify all major remaining outstanding issues by the end of the year, he said.

That call reflected the fact that the next issues to resolve will be more difficult due to possible military dimensions.

The IAEA wants credible explanations for traces of highly enriched -- or bomb-grade -- uranium that inspectors found at research sites, and intelligence on links between uranium processing, explosives tests and a missile warhead design.

CRUCIAL IRAN-EU MEETING

Iran's top nuclear negotiator Saeed Jalili said on Thursday he would meet EU foreign policy chief Javier Solana on November 30. The outcome could decide whether Iran will face wider sanctions soon for pursuing sensitive nuclear capability.

ElBaradei's remarks to the board appeared carefully balanced to incorporate Western concerns while suggesting the Iran-IAEA process deserves patience to help bring it to fruition.

He addressed Western criticism that the plan neglects U.N. demands on Iran to allow wider-ranging inspections to verify Iran is not weaponising enrichment at undeclared sites.

(As a result), our knowledge about specific aspects of Iran's current program has diminished since 2006, he said, reinforcing a point made in previous Iran reports.

(We) need ... maximum clarity not only about Iran's past program but equally, or more important, about the present.

He also stressed Iran's obligation under U.N. resolutions to suspend enrichment, now being expanded towards industrial scale.

Ali Asghar Soltanieh, Iran's envoy to the IAEA, told reporters the agency's report showed Iran had been truthful about its nuclear course but warned against further sanctions.

We will continue the mood of cooperation provided that ... peace-loving countries prevent the United States or others from making noise and creating problems and jeopardizing this constructive approach by any measure in the U.N. Security Council, he said.

Remarks to the two-day IAEA board by six world powers will hint at their positions in pending deliberations about whether to seek wider sanctions on Tehran and how tough they should be.

Washington and key allies France, Britain and Germany were expected to commend IAEA progress in illuminating Iran's past, but say Iran was not meeting a broad litmus test requiring full disclosure of present activity and a halt to enrichment.

Russia and China were likely to cast the IAEA's report in a more positive light and warn against disrupting it. Both have blocked tougher sanctions, calling them counterproductive, but have lately pressed Iran harder to be open and halt enrichment.

(Editing by Philippa Fletcher)