"There is still some work to be done on a few outstanding issues, but all parties remain committed to a second resolution in the near future," State Department spokesman Kurtis Cooper said in a statement issued after the five permanent members of the UN Security Council and Germany held a conference call to discuss a new UN Security Council resolution against Iran.

The United States and leading European countries suspect Iran is seeking to build nuclear weapons under the cover of a civilian atomic programme. Tehran denies the charge and says its programme is for generating electricity.

The new measures under discussion are a follow-up to a key Security Council resolution passed on December 23 that imposed trade sanctions on sensitive nuclear materials and technology as well as other penalties after Iran refused to suspend uranium enrichment. The sanctions would be suspended if Iran complied.

The State Department put a positive gloss on Saturday's discussions but they appeared to have fallen short of US hopes that the group -- Britain, China, France, Russia and the United States as well as Germany -- would be able to agree on the elements of a resolution during the conference call.

They had a good discussion in keeping with the positive atmosphere of their conversations last week," Cooper said in a brief written statement. "Discussions will now move to New York, where our United Nations permanent representatives (ambassadors) will take up work on the issue."

US and European diplomats have said the new sanctions are expected to include a mandatory travel ban on Iranian officials involved in the nuclear programme and an expansion of the list of banned nuclear material and technology Iran may import and export.

Also under consideration is enlarging the list of Iranian officials whose assets were frozen in the December resolution. But envoys said proposals for a total arms embargo would be dropped because of Russian objections as would a ban on visas for students studying nuclear technology abroad.

Negotiators have also discussed restricting export credits provided by governments to companies doing business in Iran. Washington has pushed for Europe to end such credits.

The United States has made no secret of its desire to get a second resolution quickly to keep up momentum in its diplomatic effort to persuade Iran to suspend its nuclear enrichment work, which can provide fuel for power plants or for bombs.

Iran has repeatedly refused to do so.

On Friday, the president of the UN Security Council said he expected the 15-member body to have a draft resolution in the coming week on additional sanctions to curb Iran's nuclear ambitions, barring last minute snags.