Bahrain and the United Arab Emirates have confiscated a number of items Iran may have sought for its nuclear programme, a development that diplomats said showed how enforcement of UN sanctions against Tehran is steadily improving.

One of the items heading to Iran, but confiscated by Bahrain was carbon fibre, the diplomats told Reuters, a dual-use material UN experts have said would be crucial if Iran was to develop more advanced nuclear enrichment centrifuge technology.

Bahrain's and UAE's confidential reports to the UN Security Council's Iran sanctions committee were politically significant, envoys said on condition of anonymity, since they highlight how more and more states were enforcing the sanctions and making it increasingly difficult for Tehran to flout them.

"The fact that these two countries are now taking steps to enforce the sanctions and reporting those steps to the UN is remarkable by itself," a senior Security Council diplomat told Reuters.

"It shows that the UN sanctions regime can work. UAE has been one of Iran's enablers. Iran's becoming more isolated."

Israeli prime minister Benjamin Netanyahu said on Sunday that Tehran was close to being able to build a nuclear bomb, and US president Barack Obama was under pressure ahead of November's election from political opponents who argue that sanctions were not doing enough to stop Iran building a bomb.

The emirate Dubai had long been one of Iran's main transit hubs because of its busy port and position as a key financial centre.

The Carnegie Endowment for International Peace think-tank wrote in July 2011 that Dubai was "a top source of Iranian imports and a key transshipment point for goods - legal and illegal - destined for the Islamic republic."

But pressure from the United States and other Western powers to crack down on Iranian sanctions violations has borne some fruit in the form of redoubled efforts to enforce the sanctions and report to the sanctions committee, Western envoys said.

The Security Council imposed four rounds of UN sanctions on Tehran between 2006 and 2010 to punish it for defying Security Council demands that it suspend uranium enrichment and other sensitive nuclear activities.

Tehran rejects charges it is developing the capability to produce atomic weapons.

Iran said its nuclear programme was intended solely for the peaceful production of electricity.

UAE officials insist that the country's policy had always been to fully abide by UN regulations and cooperate with the sanctions committee. A UAE official, who declined to be identified, played down the reports to the Iran committee.

"All incidents were reported at the time when they happened, and there has been no incident in more than a year," the official told Reuters. He did not comment further.

Bahrain's mission to the United Nations in New York did not reply to a request for comment, and officials in Bahrain were not immediately available to comment.

CARBON FIBRE

Bahrain has become increasingly annoyed with what it said were attempts by Iran to undermine its government.

The Sunni-led island, along with fellow Gulf Arab countries, have accused Shi'ite-led Iran of being behind the unrest in the region. Tehran denied fomenting problems in Bahrain.

UN diplomats said that some countries could also do more to enforce the sanctions.

They said it was important for China, Russia, India, Turkey and others to counter Iranian attempts to use their territory to circumvent international sanctions.

The UAE reported to the council's Iran sanctions committee that it had made some 15 interceptions of suspicious items bound for Iran over the last three years, diplomats said.

"Some of those items have been cleared as okay but some remain under investigation," a UN diplomatic source told Reuters.

Diplomats said that reports from the UAE, Bahrain and other countries would likely be mentioned in a briefing later this week for the 15-nation council by Colombia's UN envoy Nestor Osorio, who chairs the Iran sanctions committee.

Osorio's report was expected to leave out the names of the countries that submitted reports to the committee in keeping with council tradition on such delicate matters, envoys said.

In some cases, the UAE returned seized items to the original shipping countries, diplomats said.

Among the firms involved in the procurement efforts the UAE uncovered was Kalaye Electric Co. in Tehran, the former centre of Iran's enrichment centrifuge research and development programme, envoys said.

There were no details available on the items confiscated by UAE authorities, but the three items Bahrain intercepted included carbon fibre, a dual-use material that the UN expert panel identified in a May 2012 report as key for the further development of Iran's uranium enrichment centrifuge programme.

It remained unclear if Iran wanted the carbon fibre for its nuclear program, diplomats said.

The last round of UN sanctions adopted in June 2010 established the panel of experts to monitor compliance with the UN measures and gave countries the authority to inspect all cargo going to and from Iran and seize any banned items.

The United States and European Union have also imposed their own much more draconian sanctions.

- Reuters