DUSHANBE, Tajikistan — A US delegation walked out of a regional conference in Tajikistan on Monday after Iranian president Mahmoud Ahmadinejad lambasted US policy on Afghanistan as the source of all the country’s troubles.

Ahmadinejad launched his new tirade against Washington at a conference in Tajikistan’s capital Dushanbe, attended by leaders of Afghanistan’s neighbors as well as a US delegation led by Assistant Secretary of State Robert Blake.

“The cause of all the ills in Afghanistan is the presence on Afghan soil of NATO forces and above all those of the United States,” the Iranian president told the Regional Economic Cooperation Conference on Afghanistan (RECCA).

As the firebrand Iranian president was giving his speech, Blake pointedly led the US delegation out of the conference hall.

Encounters — even at multinational regional conferences — between the United States and Iran are extremely rare.

The two countries cut diplomatic relations in the wake of the 1979 Islamic Revolution and ties have remained severed ever since. Tensions are rising again over Iran’s nuclear program and Washington has never ruled out military action.

Ahmadinejad, whose country shares a huge border with Afghanistan, said that US forces had gone into the country with the aim of encircling the whole strategic region.

“They went into Afghanistan using the pretext of the fight against terror and now under the same slogan they are surrounding Russia, India and China,” Ahmadinejad said.

“We want foreign troops to leave Afghanistan in the shortest time,” he added.

The conference — which is also being attended by Afghan president Hamid Karzai and Pakistani counterpart Asif Ali Zardari — is the fifth such meeting since 2005 and aims to boost cooperation in rebuilding Afghanistan.