Speaking to reporters on the occasion of Memorial Day at the Manila American Cemetery at Fort Bonifacio, Makati, Mussomeli said the matter is a "bilateral issue" between the Philippines and Cuba.
"I know there was a request and it’s up to the Philippine government how they want to handle that," he said.
"But it’s a bilateral issue between Cuba and the Philippines. I shouldn’t speak on that point. It’s up to the Philippine government to decide what they want to do."
Cuba has asked the Philippines for help in extraditing Luis Posada Carriles, whom the Cubans have accused of involvement in the 1976 bombing of a Cuban airliner.
Posada reportedly fled to the US in 1985 while awaiting sentence in Venezuela.
Mussomeli said although the US has no extradition treaty with Cuba, there are "ways to extradite a fugitive," but that the legal process could be more difficult and complicated.
"There are occasions even with countries where there are no extradition treaties," he said. "Theoretically, you can still have those citizens out of your country."
However, Mussomeli did not say whether the US government would cooperate in any Philippine-Cuban effort to extradite Posada.
"It’s much more difficult and complicated, but it can happen theoretically," he said. "Whether it’ll happen in this case is something I just simply don’t know."
Asked about Cuba’s claim that Posada was working as a US government intelligence agent connected to the White House, Mussomeli said: "I don’t know if that’s true."
On Sunday, the Philippines said it would immediately act on Cuba’s request for help in extraditing Posada as soon as the Cuban embassy sends a diplomatic note to the Department of Foreign Affairs (DFA).
Foreign Affairs spokesman Gilberto Asuque said the Cuban embassy has to submit the communication to the DFA to officially inform the government of its request.
Once a diplomatic note is received, it will be discussed by the DFA’s Office of American Affairs, which oversees bilateral relations with countries in North, Central and South America.
Cuban Ambassador Jorge Rey Jimenez said on Saturday the Philippines is in a position to help out with the repatriation of Posada since it heads the Anti-Terrorism Committee of the United Nations Security Council and chairs the anti-terrorism task force of the Asia-Pacific Economic Cooperation (APEC).
Requests by foreign governments are usually coursed through diplomatic notes, he added.
Assistant Secretary for the Office of American Affairs Ariel Abadilla said they expect the Cuban embassy to submit the diplomatic note to formally request the government’s help.
Cuba’s request will also be coordinated with the United Nations before it is taken to the APEC anti-terrorism task force and the concerned government, he added.