Washington resumed talks with the Taliban in Qatar Saturday, both sides said, three months after President Donald Trump abruptly halted diplomatic efforts that could end America's longest war.

In September, the United States and the Taliban had appeared on the verge of signing a deal that would have seen Washington begin withdrawing thousands of troops in return for security guarantees.

It was also expected to pave the way towards direct talks between the Taliban and the government in Kabul and, ultimately, a possible peace agreement after more than 18 years of war.

But that same month, Trump abruptly called the year-long effort "dead" and withdrew an invitation to the insurgents to join secret talks at his US retreat at Camp David after the killing of an American soldier.

"The US rejoined talks today in Doha. The focus of discussion will be reduction of violence that leads to intra-Afghan negotiations and a ceasefire," said the US source briefed on efforts to end almost two decades of war in Afghanistan.

US envoy Zalmay Khalilzad has in recent weeks made a whistle-stop tour of countries with a stake in Afghan peace, including Pakistan US envoy Zalmay Khalilzad has in recent weeks made a whistle-stop tour of countries with a stake in Afghan peace, including Pakistan Photo: AFP / KARIM JAAFAR

The Taliban spokesman in Qatar, Suhail Shaheen, confirmed the talks on his Twitter account, saying they had resumed "from where they were broken off".

"Talks revolved around the signing of an agreement and related issues," he wrote.

"Negotiations will resume tomorrow."

Anas Haqqani, brother to the Taliban's deputy leader, participated in the talks, Shaheen confirmed.

Haqqani was released from Afghan government custody last month as part of a prisoner swap that saw an American academic and his Australian colleague freed.

During a surprise visit to a US military base in Afghanistan last week, Trump said the Taliban "wants to make a deal."

A halt to Taliban attacks is the key priority for Kabul in the resumed talks between Washington and the insurgents A halt to Taliban attacks is the key priority for Kabul in the resumed talks between Washington and the insurgents Photo: AFP / WAKIL KOHSAR

Even during the stall in talks, US negotiator Zalmay Khalilzad has in recent weeks made a whistle-stop tour of nations with a stake in Afghan peace, including Pakistan.

He recently arranged a captive swap in which the Taliban released an American and an Australian academic whom they had held hostage for three years.

The Taliban have until now refused to negotiate with the Afghan government, which they consider an illegitimate regime.

In a nod to concerns raised by Afghan President Ashraf Ghani, the US State Department voiced support for a ceasefire -- a key priority for Kabul before it enters negotiations with the Islamist insurgents.

"Ambassador Khalilzad will rejoin talks with the Taliban to discuss steps that could lead to intra-Afghan negotiations and a peaceful settlement of the war, specifically a reduction in violence that leads to a ceasefire," the State Department said on Wednesday as it announced the resumption of efforts to end the conflict.

Washington had sought to seal a political deal with the Taliban ahead of September's elections in Afghanistan.

An agreement with the Taliban is expected to have two main pillars -- a US withdrawal from Afghanistan and a commitment by the militants not to offer sanctuary to jihadists.

The Taliban's relationship with Al-Qaeda was the main reason for the US invasion nearly 18 years ago.

But the thorny issues of power-sharing with the Taliban, the role of regional powers including Pakistan and India, and the fate of Ghani's administration remain unresolved.

The Taliban, believing they have the upper hand in the war, kept up attacks even while talking to the United States.