NATO's Resolute Support mission previously gave a running tally on who controlled or was contesting Afghanistan's districts, and the percentage of the Afghan population this reflected.

US officials would frequently refer to the data to underscore battlefield success, but according to the US Special Inspector General for Afghanistan Reconstruction (SIGAR), Resolute Support (RS) now says these district-stability assessments are "of limited decision-making value to the (mission) commander".

The last data RS provided showed the percentage of Afghans living in areas controlled or influenced by the Kabul government slipping from 65.2 percent to 63.5 percent.

The downward slide undermined predictions that 80 percent of the population would be under government control by the end of this year.

SIGAR head John Sopko said the decision to withhold the data nurtured suspicion.

"When you start hiding things like this, over-classifying... You tend to create cynicism in your populace and everybody else that you're losing, or it's bad news," Sopko told journalists ahead of the SIGAR report's release.

At the request of the Afghan government, RS has also agreed to stop publishing casualty figures for Afghan security forces.

The numbers showed massive losses for the local forces, reaching several thousand per year.

SIGAR's report also noted that violence in Afghanistan had increased 19 percent between November 2018 and the end of January, compared to the previous quarter.

The uptick comes even as the United States tries to negotiate a peace settlement with the Taliban.

A new round of talks between the insurgents and US peace envoy Zalmay Khalilzad is expected to start in Qatar on Wednesday, according to the Taliban.

A possible deal to end the 17-year-old war would see foreign forces leave Afghanistan in return for the Taliban guaranteeing the country could not be used as a safe haven for terror groups.

But for an enduring peace, any deal must include the Afghan government, and so far they have not been included in talks.