The United States says it has information about serious human rights violations if Russia invades Ukraine.
"In particular, we have credible information suggesting that Russian forces are preparing lists of identified Ukrainians to be killed or sent to camps following a military occupation," US Ambassador Bathsheba Nell Crocker wrote in Geneva to the UN Human Rights Officer Michelle Bachelet.
The letter is available from the German Press Agency.
It also said the US had intelligence that "Russian forces are likely to use lethal measures to disperse peaceful protests."
The United States therefore fears that torture will be used as in "previous Russian actions".
Target would be people who would resist Russia, “including Russian and Belarusian dissidents in exile in Ukraine, journalists and anti-corruption activists, and vulnerable populations such as religious and ethnic minorities and LGBTQI+ people.”
The abbreviation stands for lesbian, gay, bisexual, trans, inter and queer people and the plus sign as a placeholder for other identities.
The US did not disclose its sources for the information.
According to media reports, the American government has intelligence information that Moscow is said to have given its military orders to proceed with plans for an invasion of Ukraine.
In the west, there are fears that Kremlin chief Vladimir Putin could use the fighting as a pretext for an invasion of the neighboring country.
According to American sources, Russia has gathered around 150,000 soldiers at the border.
However, Moscow has been denying plans of attack for weeks.