Hoped-for peace talks between the Afghan government and Taliban insurgents will not bear fruit until 2015 at best, a year after US-led troops leave the country, the EU's Afghanistan envoy warned Wednesday.

"The European Union supports an Afghan-led dialogue on reconciliation. Whatever channels they choose is up to them," Vygaudas Usackas told an open session of the Geneva Centre for Security Policy, a Swiss think-tank.

"But being realistic, I don't expect any breakthrough until 2015," said Usackas, who bows out in September after more than three years as the EU's top diplomat in Afghanistan.

Efforts to get talks off the ground hit a hurdle Tuesday when the Taliban temporarily closed their newly opened office in Qatar, blaming "broken promises" by the Afghan government and United States.

The office was opened in the Qatari capital Doha on June 18, marking a first step towards a potential peace deal after 12 years of fighting.

But Afghan President Hamid Karzai was enraged when the Taliban styled it as an unofficial embassy for a government-in-exile.

He reacted by breaking off security talks with Washington and threatening to boycott any peace process altogether.

International pressure is mounting to get talks going in an effort to end the Islamist Taliban's insurgency before 100,000 US-led troops leave Afghanistan next year.

"We're watching the situation around the Doha office... We know that peace and reconciliation requires patience and consistency," said Usackas.

The international community is also pushing the Afghan government to fight engrained corruption, and to ensure a free and fair presidential election in April, when Karzai is due to leave office.

"I hope the Afghan government is getting the message. Business as usual is no longer the norm," said Usackas.

As clean a vote as possible is seen as a key stepping stone to peace, in the wake of past ballots which earned international criticism.

"We should not expect miracles or quick fixes in the remaining months of President Karzai's administration. Afghanistan faces a complex situation. The reality is that Afghanistan will continue to be a conflict-affected and fragile state after the transition in 2014," said Usackas.

"The war may end for the international community in 2014. But the real causes of the conflict -- extremism, radicalism, illiteracy and poverty -- will persist," he underlined.