In a joint press conference with French President Emmanuel Macron, Trump called Xi a friend and a great leader he respects.
"He's a very talented man. I think he's a very good man. He loves China, I can tell you. He loves China. He wants to do what's right for China," Trump said in Paris.
He also said France and the U.S. are "forever joined together by the spirit of revolution and the fight for freedom."
But Trump's positive comments are at odds with renewed criticism of the Chinese government after the death of Liu, who had been a leading figure in the push for democracy and human rights in China.
German Chancellor Angela Merkel said in a statement that Liu had been a "courageous fighter for civil rights and freedom of expression."
Earlier Thursday, Chinese authorities said Liu died at the age of 61 from multiple organ failure. He had not been allowed to leave China to treat his late-stage liver cancer, as he had repeatedly asked to do.
Artist and fellow dissident Ai Weiwei told Reuters on Thursday that with Liu's death, "China showed how brutal its society can be."
While Liu was released on medical parole in June, he was still under government supervision. Chinese leadership also initially resisted pressure to allow foreign doctors to attend to Liu, though they eventually acquiesced. Those professionals said the activist was well enough to travel for treatment.
Beijing must bear "heavy responsibility for his premature death" for not allowing Liu to be medically evacuated, Berit Reiss-Andersen, chair of the Norwegian Nobel Committee, said in a statement.
"While the whole world watched, China chose instead to maintain the isolation of its prisoner," she said.
Following Liu's death, Secretary of State Rex Tillerson released a statement praising the activist as someone who "embodied the human spirit that the Nobel Prize rewards."
"Mr. Liu dedicated his life to the betterment of his country and humankind, and to the pursuit of justice and liberty," Tillerson said.
Foreign policy hawk Sen. John McCain said Liu's death was an "egregious" and "barbaric" violation of the activist's human rights.
"Unfortunately, and as Dr. Liu would have wanted everyone to remember today, this is only the latest example of Communist China's assault on human rights, democracy, and freedom," McCain said.
Hours after Trump's press conference, the White House released a statement that said the president was "deeply saddened to learn of" Liu's death and offered his condolences.
— Reuters contributed to this report.
Update: This story has been updated to include the White House's statement.