WASHINGTON (AP) — President Joe Biden spoke Wednesday with the wife of detained WNBA player Brittney Griner, who is on trial in Russia, to reassure her that he is working to win Griner’s freedom as soon as possible, the White House said.

Biden’s conversation with Cherelle Griner followed Brittney Griner’s personal appeal to the president in a handwritten letter from the basketball player the White House received on Monday. In the letter, Griner said she feared she would spend forever in detention in Russia and asked Biden to not “forget about me and the other American Detainees.”

Griner has been detained in Russia for four months and is currently on trial, accused of possessing vape cartridges containing cannabis oil.

The call was placed as Griner’s family has become more aggressive in pressuring the Biden administration by speaking out about her case, including through Brittney Griner’s letter to the president and several television interviews by Cherelle Griner, who said she did not think the government was doing enough to bring her wife home.

“The President called Cherelle to reassure her that he is working to secure Brittney’s release as soon as possible, as well as the release of Paul Whelan and other U.S. nationals who are wrongfully detained or held hostage in Russia and around the world,” the White House said in a statement. “He also read her a draft of the letter the President is sending to Brittney Griner today.”

Biden offered his support to the family and committed to making sure they receive “all possible assistance” while the administration pursues steps to win Brittney Griner’s release, the White House said.

Griner is in the midst of a trial in Russia that began last week after she was arrested on Feb. 17 on charges of possessing cannabis oil while returning to play for her Russian team. The trial is scheduled to resume Thursday.

Fewer than 1% of defendants in Russian criminal cases are acquitted and, unlike in U.S. courts, acquittals can be overturned.

Cherelle Griner told “CBS Mornings” in an interview Tuesday that it was “disheartening” to her that she had yet to hear from Biden during her wife’s detention.

White House press secretary Karine Jean-Pierre was asked repeatedly about Griner during her daily briefing Tuesday. She said Biden read the letter, but would not describe his reaction, other than to say, “This is very personal to him.”

Jean-Pierre did not say whether there were plans for Biden to speak with Griner’s family, but noted that National Security Adviser Jake Sullivan and Secretary of State Antony Blinken both recently had spoken to Griner’s wife.

Representatives for Brittney Griner on Monday shared excerpts from her letter to the president.

In one, she wrote, “…As I sit here in a Russian prison, alone with my thoughts and without the protection of my wife, family, friends, Olympic jersey, or any accomplishments, I’m terrified I might be here forever.”

The letter was delivered to the White House on the Fourth of July, which Brittney Griner said was a special day for her family.

“On the 4th of July, our family normally honors the service of those who fought for our freedom, including my father who is a Vietnam War Veteran,” the center for the Phoenix Mercury said. “It hurts thinking about how I usually celebrate this day because freedom means something completely different to me this year.”