With threats of new sanctions against his country swirling, Iranian President Mahmoud Ahmadinejad struck a typically defiant tone on Wednesday, calling his country's nuclear progress "irreversible," and emphasizing success at its Natanz underground nuclear site.

In a speech to loyalists, President Ahmedinejad asserted the country now has 3,000 centrifuges to enrich uranium, which could produce fuel for either nuclear reactors or a bomb, Reuters reports.

Western experts say 3,000 machines running smoothly for long periods at supersonic speed could make enough enriched uranium for an atomic bomb in about a year, if Iran wanted, and form the basis for "industrial-scale" nuclear fuel production.

"The Iranian nation has entered the phase of industrial scale of nuclear fuel [production] and the train of the Iranian nation's progress is irreversible," Ahmadinejad told a rally in South Khorasan province broadcast live on state television.

Iran now appears to have nearly 3,000 installed, divided into 18 cascades of 164 each, diplomats and analysts said, but there is still no evidence they are being run together, or that all are being fed with uranium for enrichment.

On Tuesday, US Defense Secretary Robert Gates traveled to China, partly in the hope of gaining more support for heightened sanctions against Iran. Agence France-Presse reports that China appears unmoved from its position that anything beyond diplomacy is required.

The US defence secretary made no apparent headway on an appeal for Chinese support for sanctions against Iran over its nuclear programme in his talks here Monday, when he was told China preferred diplomatic dialogue to economic pressure.

But a senior US defence official told reporters that in the meeting with Hu he would push for further discussions on Iran.

China has joined Russia, also a veto-wielding permanent member of the UN Security Council, in opposing a further round of UN economic sanctions to step up the pressure against Tehran, which has defied international demands that it halt its uranium enrichment programme.

While Russia and China, both powerful at the United Nations, appear opposed to heightened sanctions, the Bush administration is finding allies in its quest for tougher measures against Tehran. The German government broadcaster Deutsche Welle reports that during his visit to Washington this week, French President Nikolas Sarkozy expressed differences on some international issues but appeared to largely share Washington's concerns over Iran.

Sarkozy may not see eye-to-eye with Bush on policy in Iraq, but "that doesn't influence our friendship," said the French president, who also hailed US courage after the attacks on Sept. 11, 2001.

The two are in agreement, however, on the Iran nuclear standoff and Paris has repeatedly supported stronger sanctions.

"The hypothesis of a nuclear weapon in the hands of the current leaders of Iran is for France inacceptable (sic)," said Sarkozy, adding that civilian nuclear energy is a right, also for Iran.

The Associated Press reports that Iran is also embroiled in a fight to keep five of its nationals off Interpol's most wanted list. US, Argentine and other international officials allege the five were involved in a 1994 bombing that killed 85 people at a Jewish community center in Buenos Aires.

Iranian envoys at [an Interpol] meeting in Morocco on Tuesday accused Israel and the United States of playing politics with the international police agency as it considers whether to put five Iranians and a Lebanese man on its most-wanted list.

Argentine prosecutors have alleged that Iranian officials orchestrated the bombing and entrusted the Lebanon-based militant group Hezbollah to carry it out.

In March, Interpol's executive committee backed Argentina's request to put out red notices for the six, including an Iranian former intelligence chief and former leader of the elite Revolutionary Guards.

Iranian delegates lobbied colleagues by handing out dossiers written in several languages and explaining their case. Among their arguments: Argentina's investigation was flawed, if not corrupt; some witnesses cited in that probe were themselves wanted by Interpol; Iran quickly condemned the bombings; a bilateral resolution would be better.

Iran's apparent nuclear progress is stirring alarm in Israel, the Middle East's lone nuclear power and the country that feels most threatened by Iran's program. The right-leaning Jerusalem Post quotes Israeli Deputy Prime Minister Shaul Mofaz as saying that the next year will prove decisive on the question of whether Iran's nuclear progress can be halted.

"Iran's nuclear program is proceeding like an express train. The diplomatic efforts to thwart Iran are like a slow train. If we cannot derail the Iranian train from the tracks, we are on the verge of a nuclear era that will totally alter the regional reality," the former defense minister and IDF chief of General Staff told the Conference of Presidents of Major American Jewish organizations in New York.

Another warning that time is running out came on Tuesday from Brig.-Gen. Yossi Baidatz, head of Military Intelligence's research bureau, who told the Knesset Foreign Affairs and Defense Committee that if Iran's nuclear program went unchecked, the Islamic Republic could have nuclear weapons by the end of 2009.

"The Iranian regime is faced with internal issues, but there is no threat to its existence or stability. Assuming it faces no difficulties, the worst case scenario is Iran obtaining nuclear arms by 2009," said Baidatz. He added that the regime of Iranian President Mahmoud Ahmadinejad remained popular throughout the region, despite criticism farther abroad.

Others are more skeptical about Iran's nuclear progress. In the November issue of Arms Control Today, a publication of the US-based Arms Control Association, physicist and former UN weapons inspector David Albright and former State Department official Jacqueline Shire argue that, while it appears Iran is seeking nuclear weapons, it also still seems to be having technical problems.

Predicting when Iran could have nuclear weapons is more art than science. Setting aside the political decision that would precede Iran's acquisition of a nuclear weapon, the country faces the hurdles of acquiring sufficient nuclear explosive material for its first nuclear weapon and weaponizing that material into a workable, deliverable design. These hurdles are surmountable with time. Nonetheless, Iran's quest for nuclear weapons has gone more slowly than expected, given that Iran began its gas centrifuge program in 1985, at the height of the bloody Iran-Iraq War.

Examined in its totality, with all the caveats and unknowns, Iran's uranium-enrichment program still has a way to go. It has achieved the appearance of success in some areas by manufacturing and installing 3,000 centrifuges… Iran has not (yet) demonstrated competency at enriching uranium, though it is clearly on the road toward doing so.

Despite the unknowns, the day when Iran could have the capability to make significant quantities of (highly enriched uranium) is firmer and is approaching. What to do about Iran will become a higher priority in 2008 and likely dominate the agenda of the next administration, perhaps as much as Iraq has.