VIENNA — Iran's recently revealed uranium enrichment hall is a highly fortified underground space that appears too small to house a civilian nuclear program, but large enough to serve for military activities, diplomats told The Associated Press on Thursday.

Iran began building the facility near the holy city of Qom seven years ago, and after bouts of fitful construction could finish the project in a year, the diplomats said.

Both the construction timeline and the size of the facility — inspected last month by the International Atomic Energy Agency — are significant in helping shed light on Tehran's true nuclear intentions.

Iran says it wants to enrich only to make atomic fuel for energy production, but the West fears it could retool its program to churn out fissile warhead material.

One of the diplomats — a senior official from a European nation — said Thursday that the enrichment hall is too small to house the tens of thousands of centrifuges needed for peaceful industrial nuclear enrichment, but is the right size to contain the few thousand advanced machines that could generate the amount of weapons-grade uranium needed to make nuclear warheads.

The pauses in construction may reflect Tehran's determination to keep its activities secret as far back as 2002, when Iran's clandestine nuclear program was revealed.

Citing satellite imagery, the diplomats said Iran started building the plant in 2002, paused for two years in 2004 — the same year it suspended enrichment on an international demand — and resumed construction in 2006, when enrichment was also restarted.

Since then, Iran has defied three sets of U.N. Security Council sanctions aimed at forcing it to again freeze uranium enrichment.

All of the diplomats have access to information compiled by the IAEA, and demanded anonymity in exchange for discussing confidential matters with the AP.

Iran informed the IAEA only in September that it was building the facility near Qom, leading the U.S., British and French leaders to denounce Tehran for keeping its existence secret. IAEA inspectors visited the plant last month.

Iran says it fulfilled its legal obligations over when it revealed the plant's construction, though IAEA chief Mohamed ElBaradei has said Tehran was "outside the law" and should have informed his agency when the decision to construct was made.

Western officials suspicious of Tehran's nuclear program believe the Islamic Republic only decided to inform the IAEA after it became convinced that the plant's existence had been noted by foreign intelligence services.