"I would be concerned if we looked away from Russian interference in our election," Power told CNN in an interview Tuesday, days before her term ends.
"I would be concerned if a country that just lopped off part of a neighbor got to keep that," she said, referring to Trump's signals that he was open to recognizing Russia's annexation of Crimea from Ukraine, "because I think it would unleash dynamics around the globe that we can't even predict."
Power added: "I would certainly be concerned if we thought that violating human rights, murdering opposition politicians and journalists, and some of the tactics that Putin has used internally -- that that would make for a reliable partnership over time."
Trump has so far signaled a desire to foster warmer relations with Moscow, suggesting in a recent interview with The Wall Street Journal that he'd consider sanctions relief in exchange for cooperation on nuclear arms reduction.
Power, who has sparred publicly with her Russian counterpart on the UN Security Council over Moscow's annexation of Crimea, interference in Ukraine and military action in Syria on behalf of the Assad regime, said that while she hopes the next administration can expand US-Russian cooperation, it shouldn't be attempted "from the standpoint of weakness," or under what she called "terms of appeasement."
"To have historical amnesia when the stakes are this high, for us, for our shared security, for prosperity, for trade, for everything, would be a grave mistake," she said.
Power also defended the United Nations against threats by Trump and some congressional Republicans to defund the world body in response to a recent Security Council vote condemning Israeli settlements.
"Very few of the threats that we face in the 21st Century are ones that we can deal with on our own," said Power. "And when we step away from leading on the global stage, the people who take our place are not people we want leading the world."
Power and her Obama administration colleagues have been careful not to directly criticize Trump since Election Day. But as her time in office draws to a close, there are signs she may be more vocal in her post-government career.
Over the weekend, Power opened a new Twitter account, and tweeted: "We are not going gently into the night."
"I think it speaks for itself," Power said of the tweet, suggesting she and her colleagues in the Obama administration will stand up for the policies they've put in place.
"We are not going to stand on the sidelines, I think, when we see things that are making the world safer under challenge" said Power. "But by the same token, we will be the first to cheer if we see things that are making the world better."