Kabul: Influential Senator John McCain said Saturday the complete withdrawal of US troops from Afghanistan by the end of 2016 would be a "serious mistake", as stretched local forces battle a resurgent Taliban.
"I think the most serious mistake the US could make... would be to have a calendar-based withdrawal," McCain told a press conference at the NATO headquarters in Kabul.
"That would be a tragedy and in my view an opening for the Taliban to gain great success in Afghanistan," the chairman of the powerful US Senate Committee on Armed Services added.
July 4 marks US Independence Day, and McCain used the visit to meet soldiers stationed in the Afghan capital, while paying tribute to the 2,200 US troops killed there since the 2001 invasion.
NATO`s combat mission formally ended in December after 13 years, but a small follow-up foreign force named Resolute Support has stayed on.
US President Barack Obama has backpedalled on plans to shrink the US force in Afghanistan this year by nearly half, agreeing to keep the current level of 9,800 US troops until the end of 2015.
The US troops are mainly involved in training their Afghan counterparts, and make up the bulk of the 12,500-strong foreign corps.
President Ashraf Ghani thanked the United States for its support after meeting with McCain, in a statement released by the presidency.
But the current US administration would like to see a total exit for its personnel over the next 15 months, a decision McCain said required a "reassessment".
The Republican senator added that the current security situation pointed to the need for "additional US capabilities" as Afghan forces incurred significant casualties with major cities under threat.
"There`s a long, long way to go," he said.
Fighting on multiple fronts and facing record casualties, Afghan forces totalling 350,000 are struggling to rein in the militants even as the government makes repeated efforts to jump-start peace negotiations.
The Taliban`s annual spring offensive has sent civilian and military casualties soaring.
Bolstered by battle-hardened Central Asian fighters in their ranks, they recently captured the district headquarters of Chardarah, adjoining Kunduz city, triggering fears the militants would overrun their first provincial capital since 2001.
The militants also launched a brazen assault on the Afghan parliament in late June.
And in a sign of the political malaise the government is facing in its attempts to improve the country`s security situation, Afghanistan`s parliament on Saturday rejected Ghani`s nominee for defence minister for the second time.
The crucial post has sat vacant for months, reportedly due to differences between Ghani and his chief executive and former presidential election rival, Abdullah Abdullah.