"I join voices around the world in calling for the immediate release of Ukrainian politician and former air force officer Nadiya Savchenko from her illegal and unjust imprisonment in Russia," Clinton wrote in a statement initially provided to the Ukrainian Embassy on the day of Savchenko's court appearance last week.
The former secretary of state said the pilot, whose case has become a political cause in Ukraine, is being held on "trumped-up charges."
Moscow authorities contend she served as a spotter for a mortar attack that killed two Russian state television journalists in separatist eastern Ukraine in June of 2014. Savchenko, 34, served with the U.S.-led coalition in Iraq and later volunteered for a battalion that fought Russia’s invasion of eastern Ukraine. Russia annexed Crimea, a pro-Russian autonomous region of neighboring Ukraine, two years ago. Ukraine accuses Russia of also fomenting violence and encouraging separatists in eastern Ukraine.
At the time of the shelling, she was an air force officer with Ukraine's military force, which is loyal to the central government in Kiev. She was elected to the Ukrainian parliament while in jail.
Savchenko denies the murder charge and claims she was abducted by pro-Russian agents before the attack and handed over to Moscow as a scapegoat. Her lawyers say they have video and cellphone evidence showing that she was captured before the incident took place.
Protests of her treatment have claimed both that the charges are fabrications and that she should be treated as a prisoner of war, not a criminal.
The State Department has said she “reportedly endured interrogations, solitary confinement, and forced ‘psychiatric evaluation.’ ”
She began a hunger strike nearly two weeks ago to protest her confinement. On the day of her court hearing she had had no food or drink for five days. She resumed drinking water a day later, one of her lawyers told the AFP news service.
"Russia should drop all charges and release her immediately," Clinton said. "It should also meet all its commitments under the Minsk agreement to bring an end to the conflict in Eastern Ukraine, which has left thousands dead and over 1.5 million people displaced."
That was a reference to a truce agreement that the United States says Russia has ignored.
"I stand with Nadia and the Ukrainian people, as I have always stood for the rights of women and all people suffering injustices worldwide," Clinton's statement, first reported by Voice of America, said.
The Clinton campaign has not released the statement generally but provided a copy when asked about it by The Washington Post.
As secretary of state, Clinton gave special attention to issues involving the treatment of women and girls, including some human rights cases. The annexation of Crimea and fighting in eastern Ukraine came after she had left office, but she has denounced Russian actions in Ukraine.
The White House and State Department have called for Savchenko's release, as has the U.S. ambassador to the United Nations.
"Her unlawful continuing detention is a clear violation of Russia's commitment under the Minsk agreements, and she should be freed at once," Vice President Biden said in a statement last week.
"Nadiya was proudly serving her country as a member of the Ukrainian armed forces, fighting in the eastern part of the country when she was abducted by separatists and taken across the border against her will," Biden said.
A court in southern Russia is set to deliver its verdict in the case on March 21 and 22, with prosecutors seeking a sentence of 23 years.