Iran, which has increased its influence in Lebanon by supporting Hezbollah and in Iraq after toppling of Saddam Hussein, has also been making inroads into Afghanistan, a media report said on Wednesday.
Since the United States and its allies ousted the Taliban in 2001, Iran has taken advantage of the central government's weakness to pursue a more nuanced strategy: part reconstruction, part education and part propaganda, the New York Times reported.
Iran has distributed more than 200 million dollars in the country. It has set up border posts against the heroin trade, and next year will begin work on new road and construction projects and a rail line linking the countries.
In Kabul, its projects include a new medical center and a water testing laboratory.
Two years ago, the Times said, foreign engineers built a new highway through the desert of western Afghanistan, past this ancient trading post and on to the outside world.
Nearby, they strung a high-voltage power line and laid a fiber-optic cable, marked with red posts, that provides telephone and Internet access to the region.
Iranian radio stations are broadcasting anti-American propaganda into Afghanistan.
Moderate Shiite leaders in Afghanistan say Tehran is funneling money to conservative Shiite religious schools and former warlords with longstanding ties to Iranian intelligence agencies.
And as the dispute over Iran's nuclear program has escalated, Iranian intelligence activity has increased across Afghanistan, the paper says quoting American and Afghan officials.
This has included not just surveillance and information collection but the recruitment of a network of pro-Iranian operatives who could attack American targets in Afghanistan.
The paper quotes Western diplomats as saying that Iran's goals in Afghanistan are to hasten the withdrawal of American troops, prevent the Taliban from regaining power and keep the Afghan west firmly under Tehran's sway.
"Keep this area stable, but make it friendly for them," said a senior European diplomat in western Afghanistan.
American officials told the Times that they are watching closely, and no evidence has emerged of recent arms shipments to Iranian proxies, as there have been in Iraq, or of other efforts to destabilise the country.