Washington has called on Russia to immediately release Nadiya Savchenko, the Ukrainian pilot who was captured in eastern Ukraine and later handed over to Russia, where she is charged with killing two Russian journalists.
U.S. State Department spokeswoman Jen Psaki said on October 29 that Savchenko's pretrial detention in Russia, which was extended this week by a Moscow court, was "an outrage" and violated Russia's commitments under the Minsk agreements.
Psaki also said Washington was "deeply concerned about new criminal charges expected to be filed" against Savchenko.
Savchenko was captured by pro-Russian separatists on June 18 near the eastern Ukrainian village of Metalist before turning up in Russian custody in early July.
Under Russian court orders, she has been held since October 10 for "psychiatric evaluation" at the notorious Serbsky Institute, a facility behind a wave of diagnoses used to lock up dissidents during the Soviet era.
In other news, UN Secretary-General Ban Ki-moon has condemned plans by pro-Russian separatists in eastern Ukraine to hold elections.
In a statement on October 29, Ban said the November 2 ballots in the Donetsk and Luhansk regions would breach the Ukrainian Constitution and national law.
Ban said the elections would also "seriously undermine" the Minsk peace agreement.
The vote to elect separate parliaments in Donetsk and Luhansk was scheduled in defiance of Ukraine's parliamentary elections on October 26, which were won by pro-Western parties.
Russia, however, said it will recognize the results of the separatist-run elections.
Ukrainian President Petro Poroshenko and the European Union warned that Moscow's support for the elections could wreck chances for peace.
The United States says the separatist-run ballots are illegitimate.
Meanwhile, Poroshenko's bloc is claiming victory in the October 26 parliamentary elections.
Volodymyr Hroysman, a leader of the Petro Poroshenko Bloc, was quoted as saying on October 29 the political group was leading with support from a majority of Ukrainians.
Vitaliy Kovalchuk, also from the bloc, said it will be "the basis" of a future coalition.
With 98 percent of the ballots counted on October 29, Prime Minister Arseniy Yatsenyuk's People's Front party was leading with 22.2 percent, while Poroshenko's bloc had 21.8 percent.
But Poroshenko's bloc fared better in first-past-the-post voting, and according to election commission data, was positioned to take 133 parliamentary seats compared to 81 seats for Yatsenyuk's People's Front.
Yatsenyuk earlier suggested he is likely to continue as Ukraine's prime minister after a new government is formed.
With reporting by AFP, Reuters, UNIAN, and Interfax