The Kuwaiti-born German citizen said he had brought his story to Washington to encourage greater oversight of CIA activities and force the U.S. government to acknowledge what happened to him.
"I really want to raise awareness in the Congress so that they can bring some pressure to bear and make changes," el-Masri said in German after he briefed Senate aides.
A federal appeals court in Richmond, Va., heard arguments Tuesday by el-Masri's lawyers urging the judges to reinstate his lawsuit against a former CIA director, George Tenet, and others.
Discussing the case, el-Masri told reporters, "What really matters to me is that I would like to know why this was done to me, and I want an explanation and an apology."
He added, "I think that we can all benefit from what happens in my case, including others who are still in prison in other parts of the world without the rule of law."
El-Masri alleges he was kidnapped while trying to enter Macedonia for a vacation on Dec. 31, 2003. He claims he was flown to a CIA-run prison known as the "salt pit" in Kabul, Afghanistan, where he was beaten and sodomized with an object during five months in captivity.
"The conditions that I was confronted with were not fit for a human," he told reporters. He said his food was barely edible and the water putrid.
"It was like water you left in an aquarium for years," he said. "When you took one sip, the taste stayed in your mouth for hours."
The CIA has refused to comment on el-Masri's allegations, which have put a spotlight on the intelligence agency's secret program to deliver suspected terrorists for interrogation in foreign countries. The practice has been heavily criticized by human rights groups.
El-Masri's suit was dismissed in May when a judge ruled that a trial could harm national security by revealing details about CIA activities.
El-Masri said that despite the setback, he had confidence in the courts and the U.S. justice system. He previously was denied entry into the United States when he arrived to publicize the filing of his suit last year, according to the American Civil Liberties Union, which has supported his case. In recent weeks, he was issued a visa.
ACLU lawyer Ben Wizner told the appeals court on Tuesday that el-Masri was "the public face of a publicly acknowledged program" whose basics generally have become known. Thus, the lawyer said, the case could be considered without exposing government secrets.
Justice Department lawyer Greg Katsis argued that the government properly invoked its state secrets privilege to protect information outlined in a classified affidavit that Judge T.S. Ellis III read before dismissing the suit
El-Masri's allegations also are the subject of a German parliamentary investigation that is trying to clarify when German government officials became aware of el-Masri's case and whether German security services participated in interrogations in Afghanistan.
The appeals court usually takes several weeks to issue its ruling.