Dmitry Astakhov, Associated Press
Russian Premier Dmitry Medvedev announces sanctions at the Cabinet meeting in Moscow on Thursday, Aug. 7, 2014.

UNITED NATIONS — The United States warned Russia on Friday that any further intervention in Ukraine — including under the pretense of delivering humanitarian aid — would be viewed as "an invasion of Ukraine."

U.S. Ambassador Samantha Power delivered the warning at a Security Council meeting focusing on the human rights situation in Ukraine's east where government forces are fighting pro-Russian separatists. It follows recent reports by the West and the Kiev government that accused Moscow of dispatching what NATO estimates is 20,000 troops to the frontier.

Power noted that Russia has proposed creating "humanitarian corridors" to deliver aid to the separatists.

"The humanitarian situation needs addressing, but not by those who have caused it," she stressed.

Power welcomed the Ukrainian government's creation of "humanitarian corridors" to get aid into separatist-controlled areas and allow civilians out. If Moscow wants to send aid to the separatists, she said, it should be delivered by neutral international aid organizations including the International Committee of the Red Cross.

"Therefore any further unilateral intervention by Russia into Ukrainian territory, including one under the guise of providing humanitarian aid, would be completely unacceptable and deeply alarming — and it would be viewed as an invasion of Ukraine," Power warned.

The U.S. ambassador said Russia also floated the idea again last week of sending Russian peacekeepers to eastern Ukraine.

"A Russian peacekeeper in Ukraine is an oxymoron," Power said. "At every step in this crisis, Russians have sabotaged peace, not built it, and it is particularly worrisome given Russia's purported annexation of Crimea... Peacekeepers are impartial, yet Russia fully supports Russia's armed separatists in this conflict."

Russia's U.N. Ambassador Vitaly Churkin called for an immediate end to military action in the east and lashed out at the latest U.N. report on the human rights situation in the country for being one-side and blaming "the self-defense formations for ... everything short of cannibalism."

He demanded to know why the report failed to condemn the Ukrainian security forces' use of artillery and other heavy weapons to destroy residential areas and infrastructure, especially in separatist-held Donetsk and Luhansk.