Pimentel said he was assured by US Undersecretary of State Richard Armitage that Washington would be willing to play out the role if requested by Manila.
"Armitage says if the Philippine government asks for it, ‘we will give it to them’," Pimentel said.
MILF spokesman Eid Kabalu said the Americans are welcome to broker the peace negotiations.
Kabalu, however, pointed out that Malaysia plays the primary role in the peace negotiations. He suggested the US could come in but play a supporting role to finally put an end to the decades-old separatist war in Mindanao.
Kabalu yesterday stressed the MILF leadership has yet to come out with a common stand on the proposal.
"The MILF has yet to issue (an) official stand on the matter. But time and again, the MILF would like to make it clear that the Americans (are not our) enemy," Kabalu said.
Kabalu disclosed the US Embassy in Manila extended an invitation to the MILF’s Bangsamoro Development Agency (BDA) on Jan. 13, 2003 to make known its intention to offer development and economic assistance to areas affected by the armed hostilities.
But the MILF was not able to act on the US offer, Kabalu said since it was "overtaken by events," referring to the military offensive last February that overran the rebel stronghold in Pikit, North Cotabato where over 200 rebels were killed.
The US Embassy in Manila has kept silent over Pimentel’s proposal, with spokeswoman Karen Kelley saying she has not heard about it.
Pimentel has been pushing for Washington to take the lead in brokering peace negotiations between the government and the MILF.
The opposition senator filed a proposal with the Senate calling on the US to act as peace broker in the talks.
Some MILF leaders and religious groups expressed their support over the proposal.
Kabalu also said the MILF has no qualms against Pimentel who is also pushing for federalism in moves to amend the Constitution.
"The change of government to federal from presidential of which the senator is currently pursuing, is only one of the several options available for the Bangsamoro problem. The other options are autonomy or independence," Kabalu said.
He said these options could be availed through a referendum "in Muslim-dominated communities in Mindanao" which will be supervised by the United Nations.
Kabalu stressed the MILF is "very much willing" to continue peace negotiations with the government. "It has been the policy of the MILF to pursue peaceful settlement of the political conflict in Mindanao, the reason why it agreed to go back to the negotiating table after the all-out war by then... President Joseph Estrada," he said.
After the MILF were driven out from their main stronghold in Pikit town last February, the rebels launched "retaliatory attacks" against military and civilian targets in Mindanao.
The MILF has repeatedly denied the spate of bombings in several cities and towns left over 100 people dead and over 200 wounded.
After the attack in Siocon town in Zamboanga del Norte on May 4 and the bombing of a market in Koronadal City in South Cotabato six days later, President Arroyo called off the scheduled peace talks between the government and the MILF.
Mrs. Arroyo then gave the MILF until June 1 to end "retaliatory attacks" on civilians and renounce terrorism or be branded as terrorists.