The US senator met with a long-detained Filipino opposition leader who he says was wrongly imprisoned under the previous president.
A group of U.S. legislators, including a Democrat from Massachusetts, met a former senator for more than an hour in her high-security jail cell.
They had a court-authorized meeting.
The American legislators were banned from traveling to the Philippines after they called for de Lima's release. In June, the six-year term of the president ended.
The International Criminal Court is investigating the former president's anti-drugs campaign.
Ferdinand Marcos Jr., the son of the late president Ferdinand Marcos, took office on June 30 after winning the presidential election.
The delegation met Marcos Jr. at the palace. Marcos Jr. said he looked forward to continuing the partnership with the U.S.
The top critic of the former president has been locked up for more than five years and has accused the former president and his then-deputies of faking the drug charges that landed her in jail. As a senator, she was prevented from investigating the killings under the campaign against drugs.
She was accused of receiving payoffs from imprisoned drug lords. Several witnesses have recently recanted their allegations against her, re-igniting calls for her to be freed.
In her first court-authorized jail interview since her arrest, De Lima told The Associated Press that she "cried every day, especially at night, in the first few weeks not really out of self- pity but for my family and out of disbelief." She continued to fight for human rights and the rule of law while in jail.
She issued more than 1,200 handwritten daily statements, mostly her critical thoughts on the governance of the leader of the country and her reaction to breaking news like the 2020 U.S. electoral triumph of Biden and Harris.
More than 600 proposed Senate bills and resolutions were filed from jail by her. A trial court banned her from participating in online campaigning and debates after she ran for re-election under the main opposition bloc.
She was locked away from the campaign trail and sent a photo of herself. She lost her re- election bid.
In June of this year, the chairman of the U.S. Senate Foreign Relations East Asia and Pacific Subcommittee renewed his concerns over the human rights situation in the Philippines.
The incoming administration of Marcos Jr. gave them an opportunity to reject the past and embrace policies that support the rule of law in the Philippines.
It was not known if the Philippine leader responded to the call for de Lima to be released.