Brittney Griner appeared in a courtroom in Khimki, a suburb of Moscow, on Friday morning for the first day of the WNBA star's trial in Russia, where she has been in custody for 134 days.
Griner was detained at Sheremetyevo International Airport in Russia on Feb. 17 after she was accused of carrying vape cartridges containing hashish oil, which is illegal in Russia.
The first witness at Griner's trial was a customs officer who was at the airport when she was arrested.
According to a Russian reporter inside the courtroom, who spoke with ABC News, Griner said through a translator that she understood the accusation but declined to comment on the charge, saying she will share her thoughts at a later time.
The judge began the examination of evidence with the interrogation of witnesses. Representatives of the U.S. Embassy, as well as two representatives from Russian and foreign media were allowed into the courtroom.
An American reporter inside the courtroom, who spoke with Griner, told ABC News on Monday that Griner said she is fine, but she misses her ability to work out like she used to. She also said that since she doesn't speak Russian, the court appearances are difficult for her, but she has been provided an interpreter.
As Griner left the courtroom, she did not respond to ABC News' question when asked how she's doing. The Phoenix Mercury player is expected to appear in court again for the second day of the trial on July 7.
Griner's detention in Russia was extended repeatedly, most recently through Dec. 20, which is the expected length of her trial. If convicted, Griner, 31, faces up to 10 years in prison.
Ahead of the trial, friends and family members of Griner gathered for a vigil in New York City in honor of the detained athlete on Wednesday.
"Feb 17th was the last time I talked to my sister," said Janell Roy, Griner's childhood friend. "I haven't been in communication with her, I haven't been able to talk to her and it hurts."
The U.S. government classified Griner's case on May 3 as "wrongfully detained," according to a report from The Associated Press -- meaning the United States will more aggressively work to negotiate her release even as the legal case against her plays out, the State Department said.
"... The fact remains that the U.S. Government has determined that Brittney Griner is wrongfully detained and being used as a political pawn," Griner's agent, Lindsay Kagawa Colas, wrote in a series of tweets on Monday . "The negotiation for her immediate release regardless of the legal proceedings should remain a top priority and we expect [President Joe Biden] and [Vice President Kamala Harris] to do everything in their power, right now, to get a deal done to bring her home."
White House National Security Adviser Jake Sullivan told reporters on Tuesday that Griner is "unjustly detained" and called on the Russian government to release the American basketball star.
Sullivan further stressed that the U.S. is "actively engaged" in working to secure Griner's release, but added that the diplomatic efforts are "sensitive matters."
"But I will tell you it has the fullest attention of the President and every senior member of his national security and diplomatic team, and we are actively working to find a resolution to this case, and will continue to do so without rest until we get Brittney safely home," he said. "We also are trying to work actively to return all unjustly detained Americans and hostages being held overseas, whether that be in Iran or Afghanistan or Russia or Venezuela, or China or elsewhere."
Russia's invasion of Ukraine began one week after Griner was detained. Some officials are concerned that Americans jailed in Russia could be used as leverage in the ongoing conflict.
Calls to free Griner escalated following the release of U.S. Marine veteran Trevor Reed in April, who was freed from a Russian prison as part of a prisoner exchange. Former Marine Paul Whelan has also been detained in Russia since 2019.
Griner's wife, Cherelle Griner, told "Good Morning America" co-anchor Robin Roberts in May that she would like to speak with President Joe Biden.
"I just keep hearing that, you know, he has the power. She's a political pawn," she said. "So if they're holding her because they want you to do something, then I want you to do it."
Asked about a potential meeting between Cherelle Griner and President Biden last week, White House press secretary Karine Jean-Pierre said, "We don't have anything to share about a potential phone conversation or meeting."
ABC News' Shannon Crawford and Molly Nagle contributed to this report.