Here are 10 developments in the story:
The two countries decided in 2003 to develop Chabahar on the Gulf of Oman, near Iran's border with Pakistan.
The port in southeast Iran will allow India to bypass Pakistan to transport goods to Afghanistan and central Asia using a sea-land route.
Pakistan does not allow India to send goods through its territory to Afghanistan and has only recently begun to allow a trickle of Afghan exports to cross through to India.
The Chabahar project moved slowly because of the sanctions over Iran's nuclear programme, which have now been removed.
The two countries maintained a close relationship despite the US-led trade restrictions that halved their oil trade to 220,000 barrels per day in 2014.
India wants to develop the port as a counter to Pakistan's Gwadar port, which was built with Chinese assistance and is 72 km from Chabahar.
In February, the government cleared a 150 million dollar line of credit and the formation of a company in Iran to handle the project.
Sushma Swaraj, on a four-day tour of Iran and Russia, yesterday met Iranian President Hassan Rouhani and said in a statement that he had spoken of Chabahar as a defining partnership which has the potential of connecting the entire region.
Chabahar is the first foreign port that India is directly involved in developing; it has the capacity to handle 2.5 million tonnes a year.
Chabahar is officially designated as a Free Trade and Industrial Zone by Iranian government. Due to its free trade zone status, the city has increased in significance in international trade.
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