This will be the first visit by Mukherjee to a country outside India's immediate neighbourhood and the first visit by a senior Indian functionary since New Delhi voted against the Iranian nuclear programme twice at the International Atomic Energy Agency (IAEA) over the last 18 months.

K. Natwar Singh was the last Indian foreign minister to visit Tehran in September 2005.

Mukherjee's visit will be closely watched in the US that enacted a law last month to open the doors of global nuclear commerce with India in return for New Delhi placing 14 of its 22 nuclear reactors under international safeguards and cooperating with Washington on isolating and dissuading Tehran from developing nuclear weapons.

The pricing of gas through a $7 billion tri-nation pipeline facilitating the supply of Iranian gas via Pakistan to India will figure prominently in discussions. The three countries are said to have agreed on a pricing formula of the Iranian gas - a subject of intense negotiations for the past few months - at a meeting in Tehran last month.

Besides the trans-national pipeline, Mukherjee will also discuss with his counterpart Manouchehr Mottaki the precarious security situation in Afghanistan in whose stability both countries have significant stakes.

Significantly, Mukherjee's trip to Tehran takes place weeks after Prime Minister Manmohan Singh and visiting Russian President Vladimir Putin discussed the Iranian issue and agreed to cooperate to find "an effective solution" to the Iranian nuclear standoff through "political and diplomatic efforts."

India has backed Iran's peaceful use of nuclear energy but has defended the vote against the Iranian nuclear programme, arguing that a nuclear-weapon Iran is not in its national interests.

Mukherjee's visit has domestic dimension as well with some political observers pointing out that the visit is aimed at winning support of the sizeable Shia population in Uttar Pradesh that goes to polls in a few months.

The Iranian nuclear issue will figure prominently in a trilateral meeting of Indian, Russian and Chinese foreign ministers later this month here after Mukherjee returns from Tehran.