The U.S. has “credible information” indicating that Russia is creating lists of specific Ukrainians “to be killed or sent to camps following a military occupation,” a top diplomat told the United Nations in a letter obtained by the Washington Post on Monday.

The letter to the United Nations High Commissioner for Human Rights Michelle Bachelet warns that those who could be targeted include Russian and Belarusian dissidents in exile in Ukraine, journalists, anti-corruption activists, and religious and ethnic minorities. While the warning to the U.N. does not provide details about the information obtained by the U.S., it claims “human rights violations and abuses in the aftermath of a further invasion are being planned.”

The Washington Post reported on the letter on Sunday.

“We are deeply concerned about Russia’s continuing human rights abuses in the parts of Ukraine it already occupies and have every reason to believe those concerns will multiply following a new military offensive,” wrote Ambassador Bathsheba Nell Crocker, the U.S. representative to the U.N. and other international organizations in Geneva.

The letter continued: “These acts, which in past Russian operations have included targeted killings, kidnappings/forced disappearances, unjust detentions, and the use of torture, would likely target those who oppose Russian actions.”

Crocker said the U.S. also has information that Russian forces “will likely use lethal measures to disperse peaceful protests or otherwise counter peaceful exercises of perceived resistance from civilian populations.”

The U.N. Office for the High Commissioner for Human Rights said it received the letter Monday morning and is reviewing it.

“Over the past few days, the situation on the ground has begun to deteriorate, with increasing human rights risks,” the office said. “There has been a significant increase in exchanges of fire across the contact line from 17 February, including the use of heavy weapons. We call on all parties to immediately and fully respect the ceasefire. It is critical that all governments contribute to the de-escalation of tensions by engaging in diplomacy and good-faith dialogue.”

Asked Sunday about the list of Ukrainians that could be targeted by Russia and whether she is concerned for her safety, Ukrainian Ambassador to the U.S. Oksana Markarova told “Face the Nation” that “we all are concerned about Ukraine and there are so many Ukrainians that are ready to resist and fight.”

“Whatever crimes they’re willing to commit in order to kill some of us, it will not stop others and it will not help their cause,” she said.

Russia has massed roughly 150,000 troops around Ukraine, escalating concerns from the U.S. and western allies that an invasion is imminent.

President Biden on Friday told reporters he is “convinced” Russian President Vladimir Putin made the decision to invade, with an attack expected in the “coming days.”

A U.S. official told CBS News that intelligence indicated Russian commanders have received orders to proceed with an invasion and were making specific plans for how they would maneuver in their sectors of the battlefield. The orders, however, don’t mean an invasion of Ukraine is a certainty, as Putin could still change them if he changes his mind, according to the official.

Amid the heightened tensions and warnings that a Russian attack is likely, the Biden administration has continued to push Moscow to pursue a diplomatic option to prevent a war with Ukraine.

Secretary of State Antony Blinken is set to meet with his counterpart, Russian Foreign Minister Sergey Lavrov, on Thursday in Europe if Russia doesn’t launch an invasion. Mr. Biden has also agreed “in principle” to meet with Putin if an invasion hasn’t happened, the White House said Sunday.

The Kremlin said Monday it’s “premature” to discuss concrete plans for a summit between the two leaders, but said a meeting is “possible if the heads of state consider it appropriate.”