The Iranian Foreign Minister, Kamal Kharrazi, said he hoped the Taleban would release the detainees before it was too late, as he put it.

Iran believes its diplomats are held in Mazar-e-Sharif

Iran says several of its citizens, including diplomats, were captured by the Taleban after they took the northern Afghan city of Mazar-e-Sharif last month.

"The Taleban must accept all the responsibility for their action and resolve the matter as quickly as possible," Mr Kharrazi said.

US concern

The United States has expressed concern at the build-up of Iranian troops on the Afghan border and has urged Tehran not to take military action.

Some 70,000 troops took part in military exercises near the Afghan border. Iran has announced its troops will remain there at the end of the exercises "to defend its interests against foreign threats".

State Department spokesman James Rubin said the two sides should resolve their dispute peacefully under United Nations mediation.

"We are urging restraint by all sides. We want Afghanistan's neighbours to refrain from taking actions that could further enlarge or inflame the conflict, and obviously, to respect its international borders," he said.

UN involvement

The Iranian foreign minister said he expected UN Secretary-General Kofi Annan to send a fact-finding team, including Iranians, to Afghanistan soon to try to determine the fate of the missing Iranians.

Mr Annan has held discussions regarding the status of Iranians who disappeared in Afghanistan, a UN spokesman said Tuesday.

"There are some discussions under way on a means to investigate the whereabouts or fate of the 10 Iranian nationals and one journalist who disappeared," UN spokesman Fred Eckhard said.