Iranian President Mahmoud Ahmadinejad and his Pakistani counterpart Asif Ali Zardari arrived in Tajikistan on Saturday for regional security talks with Afghan leader Hamid Karzai.

The three are due to sit down with their Tajik host Emomali Rahmon on Sunday while a top US official is also due to meet diplomats from Pakistan and Afghanistan to discuss the outcome of Karzai's February visit to Islamabad.

Neither Ahmadinejad nor Zardari spoke to reporters as they headed into separate meetings with the Tajik president.

The capital of the former Soviet republic has become a venue for top-level discussions on issues ranging from the repercussions of the war in Afghanistan to the rise of Islamic militancy and drug trafficking.

The weekend events are officially being staged in celebration of the Iranian New Year holiday Nowruz.

But the US embassy in Dushanbe said Washington's pointman on Afghanistan and Pakistan would be using the occasion to meet Sunday with Afghan Deputy Foreign Minister Jawed Ludin and Pakistan's Foreign Secretary Jalil Abbas Jilani.

US representative Marc Grossman will discuss efforts "to promote a credible Afghan-led and Afghan-owned peace process for reconciliation and durable peace in Afghanistan", the US embassy said in a statement.

On his return from Islamabad last month, Karzai invited the Taliban leadership to direct talks with his government while urging Pakistan to help negotiate efforts toward ending 10 years of war.

The Taliban militia broke off contacts with the United States last week due to a row over a prisoner swap.

US Secretary of State Hillary Clinton said Wednesday that Washington was keeping the door open to talks with Taliban and remained committed to seeking a political solution that allowed NATO troops to leave by the end of 2014.

Tajik officials said the meeting with Ahmadinejad focused on Iranian investment in the impoverished mountain republic and the prospects of new road and rail links.

Ahmadinejad is also due to attend an Afghan economic recovery conference in Dushanbe on Monday.