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 the family his support and committed to making sure they receive “all possible assistance” during the administration’s pursuit of Brittney Griner’s release, the White House said.

Vice President Kamala Harris also spoke with Cherelle Griner.

Griner, 31, 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. She could face 10 years in prison if convicted of large-scale transportation of drugs.

The trial was 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.

A representative for Cherelle Griner did not immediately respond to a text message from The Associated Press. Cherelle Griner was scheduled to speak publicly Wednesday night at a rally in Phoenix organized by Brittney Griner’s WNBA team.

White House press secretary Karine Jean-Pierre told reporters on Wednesday that Biden “has been clear about the need to see every American who is wrongfully detained or held hostage abroad released, including Brittney Griner.”

“This has been top of mind for the president,” she said. Jean-Pierre added that Biden is updated daily on the status of efforts to win freedom for Brittney Griner and other Americans the U.S. government believes are being wrongfully detained in Russia and elsewhere.

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 is 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.”

Griner’s supporters have encouraged a prisoner swap like one in April that brought home Marine veteran Trevor Reed in exchange for a Russian pilot convicted of drug trafficking conspiracy.

Russian news media have repeatedly speculated that she could be swapped for Russian arms trader Viktor Bout, who is serving a 25-year sentence on conviction of conspiracy to kill U.S. citizens and providing aid to a terrorist organization.

Russia has agitated for Bout’s release for years. But the wide discrepancy between Griner’s case — involving alleged possession of vape cartridges containing cannabis oil — and Bout’s global dealings in deadly weapons could make such a swap unpalatable to the U.S.

Others have suggested she could be traded along with Whelan, a former Marine and security director serving a 16-year sentence on an espionage conviction that the U.S. has repeatedly described as a setup.