U.S. President Barack Obama accused Iran of building a secret nuclear fuel plant and demanded Tehran immediately halt what he called a “direct challenge” to the international community. Obama went public with the charge at a Group of 20 (G-20) Summit in Pittsburgh, Sept. 25, Reuters informs.

British Prime Minister Gordon Brown and French President Nicolas Sarkozy joined Obama’s statement.

“It is time for Iran to act immediately to restore the confidence of the international community by fulfilling its international obligations,” Obama said, adding that Tehran had been building the plant in secret for years.

The International Atomic Energy Agency (IAEA) said Iran — that insists its nuclear program is for peaceful purposes to generate electricity — had disclosed the existence of the plant to IAEA Director-General Mohamed ElBaradei on Monday. The disclosure, extending a history of Tehran withholding sensitive nuclear plans from U.N. nonproliferation inspectors, gave grist to Western calls to consider tougher U.N. sanctions against Iran ahead of October 1 talks with six world powers.