Iran has postponed until 2014 the planned start-up of a research reactor which Western experts say could potentially offer the Islamic Republic a second route to produce material for a nuclear bomb, a U.N. report showed, according to Reuters.

Tehran has continued to install cooling and moderator circuit piping in the heavy water plant near the town of Arak. Nuclear analysts say this type of reactor could yield plutonium for nuclear arms if the spent fuel is reprocessed, something Iran has said it has no intention of doing.

But the country has now delayed the planned timetable for bringing Arak on line by about half a year from the third quarter of 2013, according to the latest U.N. information in a confidential report submitted to member states late on Friday, November 16.

The Arms Control Association, a Washington-based research and advocacy group, said it was questionable whether Iran would be able to meet this new target date as well, in view of "significant delays and impeded access to necessary materials".

The West's worries about Iran are focused largely on underground uranium enrichment plants at Natanz and Fordow, but experts say Arak is also a possible proliferation concern.

Iran, rejecting Western allegations it seeks to develop a capability to assemble atomic arms, says its nuclear program is entirely peaceful and that the reactor will produce isotopes for medical and agricultural use.

Israel, believed to be the Middle East's only nuclear-armed state, sees Iran's nuclear program as a serious danger and has threatened to attack its atomic sites if diplomacy fails to resolve the decade-old dispute.