A United Nations rights rapporteur told AFP Monday she intended to visit the Philippines to investigate President Rodrigo Duterte's deadly war on crime, but was seeking security guarantees for people she planned to speak with.
Duterte last week said, he would allow UN and EU experts to look into the thousands of killings since he took office on June 30, 2016.
However, he also challenged them to face him in public debates.
While the government has yet to issue formal invitations, the UN rapporteur on extrajudicial, summary or arbitrary executions, Agnes Callamard, said she would solicit one.
"I welcome the reports recently (conveyed) through the media that the president and government of the Philippines will invite a UN mission to investigate the alleged extrajudicial executions," Callamard said in a statement emailed to AFP.
Callamard said, she would insist on a range of measures to ensure that those who spoke with her did not face retribution.
"The date and scope of the fact-finding mission will be discussed and negotiated with the government, along with essential guarantees," she said.
Those would include "my freedom of movement and freedom of inquiry and the assurance that those who cooperate with me will not be the object of retaliation, such as intimidation, threats, harassment or punishment," she said.
Duterte won the presidential election in a landslide in May after promising to kill 100,000 criminals as part of a campaign against illegal drugs.
More than 3,300 people have been killed since Duterte took office, police figures show.
Duterte has, in recent months, urged police and even civilians to kill drug addicts as well as traffickers and vowed to protect lawmen from prosecution.
However, he has also insisted that he has not encouraged anything illegal.
Police say, they shot dead about a third of the people killed so far in self defence, while the others were victims of intra-gang wars.
However, rights groups say, police are conducting extrajudicial killings and unleashing hired assassins and that people with no links to the drug trade are being murdered as the rule of law crumbles.
The United Nations, the European Union, the United States and international human rights groups have all condemned the killings.
But Duterte has insisted he must continue his bloody crackdown to stop the Philippines from becoming a narco state.
He often responds to criticism with abusive and defiant language.
Targets of his tirades have included US President Barack Obama, UN chief Ban Ki-moon and the European Union.