The chief prosecutor at the International Criminal Court (ICC) says he is gathering information about possible war crimes in Afghanistan.
Luis Moreno-Ocampo says that he will be examining claims relating to both Nato soldiers and Taliban insurgents.
He said the court had received allegations from many sources, relating to attacks and collateral damage.
But the court will only become involved if Kabul or the UN Security Council ask it to look into allegations.
Afghanistan signed the treaty that established the Hague-based court.
Any war crime committed on its territory by either Afghan nationals or foreign forces can be investigated by the court.
The ICC began operating in 2002 and is the world's first permanent war crimes tribunal.
Under the treaty, the court can step in only when countries are unwilling or unable to dispense justice themselves for genocide, crimes against humanity or war crimes.
Mr Moreno-Ocampo said that a preliminary examination of alleged war crimes in Afghanistan was "exceedingly complex" and time-consuming because of the difficulty of gathering information.
Both Nato soldiers and the Taliban may be investigated
But he said non-governmental organizations (NGOs) active in the country had supplied him with information and evidence.
He said he has requested information from human rights groups and groups inside Afghanistan as well as the Afghan government - and would be "very open" to information from foreign governments.
Mr Moreno-Ocampo declined to provide details on what incidents the ICC was looking into and said there was no certainty that the court would charge anyone.
'Error of judgement'
"Before we open an investigation, my office has a duty to conduct preliminary examinations to define exactly whether or not I should open an investigation," Mr Moreno-Ocampo said.
There is increasing concern over Afghanistan's deteriorating security
"What we are trying to assess is... different types of allegations, including massive attacks, collateral damage exceeding what is considered proper, and torture."
Mr Moreno-Ocampo said that there would be no need for an ICC investigation if the Afghan authorities launched credible proceedings of their own.
Last week Afghan President Hamid Karzai described a Nato air strike in Afghanistan which killed scores of civilians as a major "error of judgement."
Afghan officials have frequently complained about other Nato attacks which they say have resulted in large numbers of civilian casualties.
Nato in turn has accused the Taliban and al-Qaeda of various criminal acts in Afghanistan, including attacking schools, using civilians as human shields and kidnapping and murdering aid workers and innocent civilians.
The United States has the most troops in Afghanistan. It is not a member of the ICC and American officials have long argued that US soldiers abroad should be subject to US law, not international treaties.
Correspondents say that while members of President Barack Obama's administration have spoken more positively about the court than their predecessors, it is doubtful that US lawmakers would ever agree to give a foreign court blanket jurisdiction over US troops.
Mr Moreno-Ocampo said his staff were also engaged in preliminary enquiries on possible war crimes in Georgia, Colombia, Kenya, the Ivory Coast, and by Israeli forces in Gaza.