The total number of deaths in Afghanistan's conflict was listed at 19,694 in 2017, according to figures.
Afghanistan's drawn-out conflict could be deadlier in 2018 than the war in Syria, experts have warned.
Despite the violence in Afghanistan seemingly appearing less frequently in the media, 17 years after the US-led invasion, the country's conflict could prove the deadliest in the world this year in terms of fatalities.
The total number of deaths in Afghanistan's conflict has risen significantly year-on-year since 2013 and was listed at 19,694 in 2017, according to the Uppsala Conflict Data Program (UCDP) figures.
Afghanistan's soaring casualties and the potential end in sight for the conflict in Syria both play a part in the countries' switchover, according to Johnny Walsh, an Afghanistan expert at the United States Institute of Peace, in an interview with AFP.
In Afghanistan, "most years have become the new 'most violent year'. This is continually getting worse," he said.
Graeme Smith, a consultant for the International Crisis Group, told the news agency that some indications "suggest the Afghan war is on track to inflict more than 20,000 battle deaths in 2018," including both civilians and combatants.
He said this would "exceed the toll of any other conflict, possibly even the war in Syria."
The number of Afghan civilian deaths hit a record 1,692 in the first six months of 2018, according to a July report from the UN Assistance Mission in Afghanistan (UNAMA).
Figures for fatalities in the Afghan security forces were not available after Washington accepted a request from Kabul last year to classify the information.
NATO pulling out of the country in 2014, along with the emergence of the self-proclaimed Islamic State group in the same year, are two reasons why a rise in deaths can be seen in UCDP figures.
In 2018, long-delayed parliamentary elections, planned for October, have caused more violence, with the government trying to engage the Taliban in ceasefires and peace talks.