FACTBOX: Outlook in standoff over Iran's nuclear program

(Reuters) - The U.N. nuclear watchdog said on Friday Iran was being more transparent about its nuclear program but doubts remained about whether it was entirely for peaceful purposes and not to make atomic bombs.

Iran has revealed some nuclear advances earlier off-limits to U.N. inspectors, but a failure to clarify explosives and missile work relevant to atom bombs is a "serious concern", the International Atomic Energy Agency said.

Here are some details on what may follow in the international dispute over Iran's nuclear activity:

* IAEA-IRAN RELATIONS:

-- International Atomic Energy Agency (IAEA) director Mohamed ElBaradei hopes to resolve remaining questions about Iran's nuclear development by the next session of the IAEA's 35-nation board of governors March 3-7.

-- ElBaradei said one crucial requirement was for Iran to implement the IAEA's Additional Protocol, which allows snap inspections that could verify that Tehran is not engaged in secret bomb work beyond declared civilian atomic energy sites.

-- Last month, Iran gave ElBaradei information on its development of advanced enrichment centrifuges for the first time. ElBaradei also won agreement from Iran to answer questions about its past covert nuclear work within four weeks -- by mid-February.

-- The IAEA report issued on Friday said Iran had failed to clear up all outstanding questions by the agreed deadline. The report may be branded negative on balance by big powers and spur the U.N. Security Council to adopt more sanctions as early as next week.

-- Senior diplomats from Britain, France, Germany, the United States, China and Russia will meet in Washington on Monday to discuss next steps regarding Iran's nuclear program, a Western diplomat at the United Nations in New York said.

* SANCTIONS:

-- A U.S. National Intelligence Estimate (NIE) report released last month took U.S. friends and foes by surprise after years of strident rhetoric from Washington accusing Iran of pursuing a covert nuclear weapons program.

-- The NIE said Iran stopped actively trying to "weaponize" nuclear material in 2003 but also that it still seeking to perfect production of enriched uranium, a process that could be eventually reconfigured to make bombs if Iran so decided.

-- The NIE's findings slowed a U.S.-led push for tougher U.N. sanctions against Iran in the near future. Russia and China, both commercial partners of Iran, have hardened their opposition to tougher sanctions since the report. However on Thursday, France and Britain formally submitted a third sanctions resolution against Iran to the U.N. Security Council, on which they hope for a vote next week.

-- Iran has said it has satisfactorily answered all relevant IAEA questions about past activities, its nuclear slate is now clean and sanctions are unjustified and illegal.

(Writing by David Cutler, London Editorial Reference Unit)