The freight train service would take cargoes from Bayannur in the Inner Mongolia Autonomous Region to Tehran.
China sent an inaugural train toward Iran carrying 1,150 tonnes of sunflower seeds. It would travel a distance of around 8,000 kilometers through Kazakhstan and Turkmenistan and would arrive in Iran within two weeks.
The new train route will shorten transportation time by at least 20 days compared with ocean shipping, according to a report by Xinhua news agency.
Bayannur is China' biggest sunflower seed production area. The city exports about 180,000 tonnes of sunflower seeds every year, with 90 percent of them headed for Middle Eastern, European and US markets, the report added.
The launch of a train service to Iran comes as the United States is preparing to impose what President Donald Trump has described as a tough regime of sanctions against the country.
Establishing new train routes toward the Islamic Republic is accordingly seen as a gesture by Beijing that it wants to maintain trade with its biggest trade partner even when the sanctions are put into effect.
“While the United States is now urging foreign companies to wind down their operations in Iran, China appears to be doing the opposite,” wrote the Washington Post in an analysis.
“Thursday’s launch of a freight train connection was only the latest measure that Beijing has taken to intensify trade relations with Iran, and there seem to be no plans so far to give in to US demands.”
In February 2017, China also launched a long-distance train service that would take cargoes from its east to Iran through a route of above 10,000 kilometers - what could be one of the world's longest rail routes.
A train sent through the key connectivity project took 14 days to reach Iran after travelling through Kazakhstan and Turkmenistan.
The shipment period was almost a month less than the sea route from Shanghai to the Iranian port of Bandar Abbas.
Iranian officials have indicated that the ultimate aim is to extend the rail route to Europe, positioning Iran on a key stretch to the continent, the Guardian wrote in an analysis on the development.
These are seen as part of China’s efforts to revive the ancient Silk Road – a trans-Asian trade route that connected the east to Europe and the Mediterranean Sea.