KABUL: US Secretary of State John Kerry arrived in Kabul Saturday on an unannounced visit to encourage the revival of peace talks with the Taliban and show support for Afghanistan's beleaguered unity government which he helped create 18 months ago.

His visit comes as the Afghan Taliban is experiencing a resurgence following the withdrawal of US-led combat troops in 2014, announcing recently it was preparing for “decisive” battles in its upcoming spring offensive.

Speaking ahead of a meeting with Afghan Foreign Minister Salahuddin Rabbani, Kerry said: “We'll clearly reaffirm the strength of our bilateral ties through today's session”, adding his support for a “democratic and increasingly prosperous Afghanistan”.

He is later set to meet Afghan President Ashraf Ghani and Chief Executive Abdullah Abdullah, who were sworn to power in September 2014 three months after a tainted election led to the formation of a unity government in a deal brokered by Kerry.

Kerry's first port-of-call was NATO headquarters, where he met with General John Nicholson, the newly appointed head of the alliance's Resolute Support mission, and US troops.

The United States currently has some 9,800 soldiers in the country who have been officially limited to a training and advisory role since the end of their combat mission in 2014.

He warned: “Obviously there is no time to relax, vigilance has to be constant. “Kerry's meetings with Afghan leaders will relate to security, defence, democracy, governance, as well as economic and social development, according to a State Department spokesman.

Political and security challenges

Hopes for peace and economic stability were high following the 2014 presidential election, which marked the first democratic transition of power following the departure of Hamid Karzai who had ruled the country for almost a decade.

But 18 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.

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.

Several ministers have resigned in recent months because of the tensions between the two camps.

One of the most high-profile resignations was Ghani's number two, the former interior minister Noor-ul-Haq Ulumi who left office in February. His successor, Taj Mohammad Jahid, was confirmed by parliament on Saturday morning.

Both Ghani and Abdullah claimed victory in the presidential election, leading to a three-month stalemate until a breakthrough deal mediated by Kerry.

The delay in legislative elections is also due to the Taliban's resurgent campaign of violence, which they stepped up following the withdrawal of NATO combat troops in 2014.