Vienna, Sep 25 (DPA) Iran has told the International Atomic Energy Agency it is building a second, previously unknown, uranium enrichment plant, the IAEA confirmed in Vienna Friday.

Iran admitted to the site after finding out that Western intelligence agencies knew about the project, a diplomat briefed on intelligence findings said.

US President Barack Obama, British Prime Minister Gordon Brown and French President Nicolas Sarkozy were planning to issue a statement on this in Pittsburgh at the summit of the Group of 20 major economies later in the day, according to a diplomat of one of the involved countries.

The revelation came at a sensitive juncture in Tehran's relations with China, Britain, France, Germany, Russia and the US, which are preparing for talks with Iran on Oct 1 in Geneva, aimed at improving relations, but also at touching on that country's controversial nuclear programme.

At the same time, Obama won support from China and Russia this week for considering new sanctions against the Islamic state, should the six countries' Geneva talks with Iran not bear fruit.

Until now the international community was only aware of the operating enrichment plant in Natanz, which some countries fear could one day be used to make material for nuclear arms.

Under IAEA regulations, Tehran would have been obliged to inform the nuclear agency about such projects as soon as a decision is taken to build it. However, Iran has previously declared it is not following this rule.

The new facility is located near Qom, a town south of Tehran, the diplomat briefed on the intelligence said, and is big enough to house 3,000 centrifuges.

'That is what is needed to make (material for) a bomb a year, but not enough for a nuclear reactor,' he said.

Tehran maintains that it is enriching uranium only as fuel for nuclear electricity generation.

The information about the Qom site was contained in a letter sent Monday to the Vienna-based IAEA. The letter did not provide the location of the new plant, but said additional information would be provided 'in an appropriate and due time'.