Presidential Spokesman Ignacio Bunye said the government only wants a fair treatment of the probe into the killings.
"We are an ally of the United States in democracy and the protection of human rights and we intend, as we have done in the case of all well-meaning international institutions, to be transparent and candid in these matters, whether they pertain to violations by the revolutionary left or a few misguided soldiers," Bunye said.
He said all assistance would be given to Eric John, deputy assistant secretary of state for East Asia and Pacific Affairs.
"The US State Department can expect all the assistance it needs for a balanced and fair assessment of this matter," he added.
Malacañang has consistently welcomed probes by the international community into the unexplained killings of activists and members of the media just as it did with United Nations Special rapporteur on extrajudicial killings Philip Alston last February.
During his 10-day visit to the country, the government provided Alston with all the resources he needed for his inquiry.
"We welcome the visit of a high official from the US State Department to take an extensive and objective look at this issue and we take it as an opportunity to get the facts straight for the benefit of the American people, especially Fil-Ams in the United States," Bunye said.
John, who testified in the US Senate’s inquiry into the unexplained killings in the Philippines earlier this month, is expected to arrive in Manila next month.
The Inter-Parliamentary Union is also sending a three-member fact-finding team to the Philippines in April to look into the murders.
While the government welcomed the inquiry of the US Senate as a democratic institution, it raised concern over the panelists invited, all of whom were critics of the administration.
A team of military and police officials went to the US at the time of the hearing, supposedly to make themselves available to the Senate if needed.
The team, which included PNP Deputy Director General Avelino Razon Jr., met with a number of US officials, including members of the Senate foreign relations subcommittee that conducted the inquiry.
Militant human rights group Karapatan has recorded more than 800 cases of killings involving activists but this has been challenged by the Armed Forces of the Philippines.
In previous statements, President Arroyo said she was addressing the issue of unexplained killings and has undertaken a number of measures to bring the perpetrators to justice.
The President vowed to prosecute all of those found guilty of the killings even if they belong to the AFP. – Marvin Sy, AFP