The reported visit to Russia on Tuesday of Iran's top security official and chief nuclear negotiator has been postponed indefinitely, the ISNA news agency reported on Monday.

Iranian news agencies reported earlier on Monday that Saeed Jalili was due to in Moscow on Tuesday for a three-day visit that would include meetings with President Dmitry Medvedev and other officials to discuss bilateral relations, regional and international issues.

The Fars and MEHR agencies said the trip had been postponed to allow for additional preparation.

A Russian government source confirmed to RIA Novosti earlier that Jalili would meet with his Russian counterpart, and with the Russian leadership.

Iran's IRIBNews agency said that Jalili would be accompanied by Ali Bagheri, deputy for foreign policy and security maters.

Mediators from the Iran Six, which includes Russia, are currently discussing the transition from talks to new sanctions in response to Iran's refusal to fold its controversial nuclear program.

Russia has a history of close ties to Iran, including in nuclear energy through construction of the Bushehr power plant, but is seen as having moved closer to the U.S. position on imposing new sanctions.

Iran, which is already under three sets of United Nations sanctions for refusing to halt uranium enrichment, recently announced plans to build 10 new uranium enrichment facilities. Western powers suspect it of pursuing an atomic weapons program.

The Iran Six - Russia, the United States, China, Britain, France and Germany - have long been trying to persuade Tehran to halt uranium enrichment not only through sanctions but also in exchange for economic and diplomatic incentives.

Iran Six envoys last met in New York on January 16, but in the face of Chinese resistance to a tougher course of action decided against immediate sanctions in the hope of finding new political and diplomatic solutions to the problem.