US Secretary of State John Kerry landed in Kabul Saturday on an unannounced visit to show support for the Afghan unity government and the peace process with the Taliban.

Kerry, who is due to meet with Afghan President Ashraf Ghani and Chief Executive Abdullah Abdullah, ‘will emphasise US support for the Government of Afghanistan’ and its defence forces, State Department spokesman John Kirby said.

America's top diplomat, who has been deeply involved in Afghanistan for the past few years, will also ‘express support for the Government of Afghanistan's efforts to end the conflict in Afghanistan through a peace and reconciliation process with the Taliban.’

The US has pulled out the majority of its troops in the country, with about 9,800 remaining. It has signed a ‘Strategic Partnership Agreement’ with Afghanistan and established a bilateral commission that will meet Saturday to discuss matters related to security, defence, democracy, governance, as well as economic and social development, according to Kirby.

Eighteen months after Afghanistan's present unity government was formed, ‘There have been challenges both in terms of politics, but also in terms of the resilience...of the Taliban,’ according to the US special envoy to Pakistan and Afghanistan Richard Olson.

In early March, the Afghan Taliban announced they would not participate in talks with Kabul, dashing the Afghan government's hopes of settling the war that has lasted for more than 14 years and claimed tens of thousands of lives.

A four-way group, comprising Afghan, Chinese, US and Pakistani diplomats, formed to assist the process had hoped that direct talks could be revived by the start of March, even as fighting remained in full swing across the country.

On the political front, parliamentary elections are due to be held October 15, more than a year behind schedule, due to deep differences at the highest levels of government between Ghani and Abdullah.

Both men claimed victory in last year's presidential election, leading to a three-month stalemate until a breakthrough deal mediated by Kerry.

The delay is also because of the resurgent Taliban, who have stepped up their insurgency following the withdrawal of NATO combat troops in 2014, raising fears over the safety of voters and election officials.