MOSCOW — Since Brittney Griner last appeared in her trial for cannabis possession, the question of her fate has expanded from a tiny, cramped courtroom on Moscow’s outskirts to the highest level of Russia-U.S. diplomacy.

The WNBA star and two-time Olympic gold medalist returns to court Tuesday, a month after the beginning of the trial in which she could face 10 years in prison if convicted. As the trial has progressed, the Biden administration has faced rising calls for action to win her release.

In an extraordinary move, Secretary of State Antony Blinken last week spoke to his Russian counterpart, Sergey Lavrov, urging him to accept a deal under which Griner and Paul Whelan, an American imprisoned in Russia on an espionage conviction, would go free.

Although details of the offer remain shrouded — people familiar with it have said it envisions trading Griner and Whelan for the notorious arms trader Viktor Bout — Blinken’s public announcement of a proposal was at odds with the convention of keeping prisoner-release negotiations tightly under wraps.

White House Press Secretary Karine Jean-Pierre told reporters Monday that Russia has made a “bad faith” response to the U.S. government’s offer, a counteroffer that American officials don’t regard as serious. She declined to elaborate.

Griner, speaking from the defendant’s cage in a courtroom that barely holds a dozen people, has acknowledged there were vape canisters containing cannabis oil in her luggage when she was arrested at a Moscow airport in February. But she says she had no criminal intent and that the canisters ended up in her luggage because she was packing hastily. Griner played for a Russian women’s basketball team in the WNBA off-season.

To bolster her case, her defense lawyers have called character witnesses from her Russian team, UMMC Ekaterinburg, and presented testimony from doctors that she was prescribed cannabis as a treatment for pain. Medical marijuana treatment is not legal in Russia.

Her lawyers say they hope such testimony will bring leniency from the judge, who they say has leeway to consider mitigating factors.