Guatemala has asked the UN to find out whether eight of its peacekeepers who were killed in Africa this week were on a secret mission.
Jorge Briz is demanding answers from Kofi Annan
They were killed in clashes in eastern Democratic Republic of Congo, on what the UN called a reconnaissance sortie.
However, a French newspaper claims they were on a covert operation to capture an alleged Ugandan war criminal.
The UN denied this, but said that if peacekeepers found wanted individuals, they would be arrested.
"We do not confirm that it was this type of mission," said a spokesman for the mission in New York. "It was a reconnaissance operation."
Guatemalan Foreign Minister Jorge Briz has written to UN Secretary General Kofi Annan.
"We are asking for an explanation about this controversial information... whose contents don't coincide with the information that up until now the United Nations has provided," his letter said.
Guatemalan officials say their peacekeepers should not have been participating in any covert activity.
The French newspaper Le Monde says the Guatemalan special forces members were on the trail of Vincent Otti, a leader of Uganda's rebel Lord's Resistance Army, who is wanted by the international war crimes tribunal in The Hague.
The soldiers died trying to track a suspect, say media reports
The UN has so far only said the peacekeepers were on a sweep for fighters from the LRA, which is accused of atrocities in northern Uganda and southern Sudan, when they were ambushed.
A UN military spokesman said at least 15 LRA fighters were killed in the clash, out of a group estimated to number 50 or 60.
The UN and the Congolese army are trying to rid numerous armed groups from eastern DR Congo before elections scheduled for April.
The bodies of the soldiers were being flown back to Guatemala on Friday.