Afghanistan is in danger of turning into a sanctuary once again for Islamist extremists as the West withdraws troops and shifts its attention elsewhere, a former senior CIA official warned Tuesday.

The country could even become a refuge for Islamic State jihadists now waging war in Syria and Iraq, said Robert Grenier, the former Central Intelligence Agency station chief in Islamabad and author of a new book.

Afghan President Ashraf Ghani made his first official trip to neighboring Pakistan on Friday, seeking to improve ties crucial to his hopes of reviving Taliban peace talks as U.S. troops end their 13-year war.

Ghani will hold talks with Prime Minister Nawaz Sharif and the pair are expected to watch a cricket match between the two countries on Saturday, in a public demonstration of better relations despite fraught cross-border tensions.

Former Afghan president Hamid Karzai may have brought development and relative stability to major cities, but an insurgency-wracked countryside and sky-high corruption levels mean that for many ordinary citizens he leaves behind a mixed legacy.

His successor Ashraf Ghani was sworn in this week after a prolonged and fraud-tainted election process came to an end, with Karzai using his final speech to take a parting shot at the United States.

Afghanistan will host a grand presidential inauguration on Monday, with former U.S.-based academic Ashraf Ghani taking power as NATO troops end their 13-year war without defeating the fierce Taliban insurgency.

Ghani takes over from outgoing President Hamid Karzai after a three-month standoff over disputed election results that fueled the insurgency and worsened Afghanistan's dire economic outlook.

Outgoing Afghan President Hamid Karzai used his farewell speech on Tuesday to take a parting shot at the United States, accusing Washington of waging a war against Taliban insurgents for its own ends.

Karzai rose to power with American support in 2001 after the ousting of the Taliban regime, but he has often criticized the U.S. military campaign that has struggled to defeat the Islamist insurgency that engulfed the country.

Secret election results and an uneasy power-sharing deal have raised fears that the legacy of the U.S.-led intervention in Afghanistan will be a government that lacks the legitimacy or strength to avert the risk of a return to civil war.

A vast array of foreign armies, diplomats, development experts and aid groups converged on Afghanistan after 2001 in a multi-billion-dollar effort to foster peace and progress after the harsh years of Taliban rule.

Afghanistan's disputed presidential election inched towards a possible conclusion Monday with a senior government official hailing a "breakthrough" in talks between the two candidates, who both claim to have won the vote.

Ashraf Ghani and Abdullah Abdullah have been wrangled over a power-sharing deal after the June 14 election was engulfed in allegations of massive fraud that have threatened to spark instability as NATO troops pull out of the country.

Time is pressing for Afghanistan, without a new president since June elections, to sign accords allowing NATO to carry out its post-2014 military training mission, alliance head Anders Fogh Rasmussen said Thursday.

"Time is of the essence," Rasmussen said as he arrived for a two-day NATO summit in Newport, Wales.

Outgoing Afghan President Hamid Karzai has packed up all his personal possessions and is ready to leave the palace, his spokesman said Thursday, even though the disputed election has failed to find his successor.

Karzai, who has lived in the former royal palace in central Kabul since 2002, has supervised the process of removing his precious library of books from shelves in his residence inside the heavily-fortified building.

Afghan presidential candidate Abdullah Abdullah will reject the results of a U.N.-supervised audit of the election, his spokesman said Wednesday, tipping the country deeper into crisis just a week before the scheduled inauguration.

Fears grew of a violent backlash against the eventual result after Abdullah withdrew his observers from the audit earlier Wednesday in the latest twist of a dispute over allegations of massive fraud in the June 14 election.