MANILA—A US senator has urged Philippine President Rodrigo Duterte anew to release Sen. Leila de Lima, who is nearing 3 years in detention over what he called as "dubious and politically-motivated" charges.

In a speech on the Senate floor in Washington early Thursday (Manila time), Illinois Democratic Sen. Richard Durbin said De Lima's fearlessness to speak out against Duterte's alleged extrajudicial killings had cost her freedom.

"Sen. De Lima is a former head of the National Human Rights Commission of the Philippines, and an internationally-recognized human rights champion critical of President Duterte’s extrajudicial killings. What did that lead to? Her arrest and her being sentenced and imprisoned for 3 years in jail for speaking out against the current President of the Philippines," he said.

Durbin also read an excerpt of a letter that De Lima sent to him, which gave details about the current human rights situation in the Philippines.

"As you can imagine, I may be the one currently in detention but I'm not the only victim suffering in the situation," he said.

"So are the victims of extrajudicial killings and their families. So are all defenders of human rights and ultimately, so are all of us all over the world who defend democracy and the rule of law.”

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The US senator also called on the "autocratic" Duterte to stop threatening the travel of Americans to the Philippines after he sought to ban Filipino officials involved in De Lima's detention.

"There is an easy and honorable way forward. The Duterte regime should stop threatening the travel of Americans and so many others who travel between our nations and instead ensure a quick and credible trial for Sen. De Lima," he said.

Durbin also slammed the harassment of Filipina journalist Maria Ressa, which was seen by press freedom advocates as retaliation for the latter's critical reports against the Duterte administration.

"In the end, these will be important tests of whether cherished democratic norms we share with our long-standing Filipino allies will be respected by President Duterte," he said.

Durbin was among lawmakers who passed a resolution to bar Filipino officials responsible for De Lima's arrest from entering the US.

The Philippine government responded by banning the proponents, including Durbin, from entering the country and threatening to impose visa requirements on US citizens visiting the Philippines.

De Lima has been detained since Feb. 2017 over allegations that she received payoffs from jailed drug lords during her time as justice chief.

She has repeatedly denied the allegations, blasting her detention as "political persecution."—With a report from TJ Manotoc, ABS-CBN News