Iranian President Mahmoud Ahmadinejad, seeking to boost Tehran's weight in Central Asia, met the leaders of Tajikistan and Afghanistan on Wednesday to forge closer ties among the Persian-speaking states.

Iranian President Mahmoud Ahmadinejad, right, meets with Afghan President Hamid Karzai in Dushanbe, Tajikistan, on Wednesday, July 26, 2006. Iran has sought closer ties with the ex-Soviet republics in Central Asia since they gained independence with the 1991 Soviet collapse.[AP]

But his talks with Afghan leader Hamid Karzai and Tajik President Imomali Rakhmonov, hailed by the three as a new era in their alliance, produced little substance apart from acknowledging each others' cultural proximity.

"We are united by a common language, culture and religion. It's impossible to divide us by borders or talk about our differences," he told reporters in the Tajik capital Dushanbe after talks with Karzai and Rakhmonov.

"There are a number of global threats that unite us. Security in Tajikistan and Afghanistan increases Iran's security."

Iran is keen to strengthen its position in Central Asia, a former Soviet region with Muslim traditions, as it faces growing pressure from the West over its nuclear ambitions.

But it faces tough competition there from the United States, China and Russia who are all vying for influence in the resource-rich region.

Iran's alliance with Afghanistan, where the government is bolstered by U.S. troops, is uneasy, while another source of awkwardness is Washington's warm ties with ex-Soviet Tajikistan, a key partner in its operations in neighbouring Afghanistan.

The three carefully avoided geopolitical tensions in their talks in Dushanbe, stressing security and trade as a key element in their alliance.

"Afghanistan believes that it needs cooperation among us for its economic development," said Karzai. "Our economic stabilisation and security are in the interests of all the three countries and the region as a whole."

Tajikistan's Rakhmonov, his impoverished country still recovering from a civil war in the 1990s, proposed building a road linking the three states to boost trade and develop his country's vast hydroelectricity resources.

Ahmadinejad, speaking at the opening ceremony of an Iran-sponsored tunnel in Tajikistan, said he felt at home in the fellow Persian-speaking nation whose national flag is almost identical to that of Iran.

"I look at you and I see Iranians," he told a cheering crowd at the tunnel's construction site hidden high in the mountains north of Dushanbe.

"We are united by Islam. And the tears of happiness I see in your eyes are our happiness too."