Afghanistan now has a new road linking it with Chahbahar port in Iran.
But the 200-kilometer road in Afghanistan's southwestern province of Nimroz was built with India's help so its exports could reach Afghanistan. The goods have to pass through Iran because Pakistan denies India access to Afghanistan.
Yet trade links among the countries of South Asia and with Iran are likely to expand, say experts, if there is a rapprochement between Tehran and Washington.
"The famous India-Pakistan-Iran pipeline issue becomes a reality. And of course then, depending on how the negotiations between the three take place in terms of the cost of that, it will help all three countries enormously," said Shuja Nawaz, who is with the Atlantic Council in Washington.
Nawaz was talking about a nearly $8 billion proposed natural gas pipeline that will run from Iran to India through Pakistan. He says the pipeline is bound to improve ties between India and Pakistan because of its economic benefits.
"Another big thing is that once you open up these [kind of] pipelines, then cross Pakistan trade between India and Afghanistan opens up too, and then between India, Pakistan, Afghanistan and Central Asia," he added.
The fight against Taliban extremists also would be affected by a normalization of relations, says James Clad who is at the National Defense University. Iran moved against the Taliban and al-Qaida after the 9/11 terrorist attacks against the United States.
Clad says the Bush administration failed to take advantage of the Iranian actions.
This may change now, he says.
"But I think there are interests that the U.S. and Iran have, no matter what their political leaderships are, those interests are separate from whoever is in front of the microphone, and I think those interests probably will have all kinds of impact on South Asia," he said.
And analysts such as Clad say it will take time to overcome nearly three decades of hostility.
"There is more than just one Iran," he said. "The question is how do we deal with it and how do we approach it."