(Reuters) Iran could soon increase uranium enrichment in an underground nuclear plant, diplomats say, a development that may further complicate efforts to resolve peacefully a dispute over Tehran’s atomic ambitions.

Iran has nearly finished installing centrifuges at the Fordow enrichment plant buried deep inside a mountain and is believed to be in a position in the near future to significantly step up production there of material that could be used for bombs if processed further, they said.

For more on Iran’s secret nuclear facilities, read Reza Kahlili’s exclusive report.

“They should be able to (increase production) within a few weeks,” one diplomat accredited to the Vienna-based U.N. International Atomic Energy Agency (IAEA) said on Thursday.

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