A Russian assault on Ukraine "stays a lot of a chance" yet the human expense would be "tremendous", US President Joe Biden has said.
In comments broadcast broadly, he said the US was prepared to react unequivocally to such a move.
The US president said Russia had now massed around 150,000 soldiers on the line with Ukraine.
Russia's protection serve has said a few powers have removed. Mr Biden said that this had not been confirmed.
"[Russian powers leaving] would be great, however we have not yet confirmed that. We have not yet confirmed the Russian military units are getting back to their headquarters," the US president said.
"For sure, our experts demonstrate that they stay especially in an undermining position."
Examination: Is Russia going to attack Ukraine?
EXPLAINER: Ukraine: How arranged is Russia for an assault?
Mr Biden's discourse came hours after Russian President Vladimir Putin said Moscow's security concerns ought to be tended to and treated in a serious way.
Mr Putin has consistently denied he is arranging an attack, and said Russia didn't need one more conflict in Europe. Nonetheless, pressures have been ascending since November.
Russia has profound social and notable binds with Ukraine, which is a previous Soviet republic.
Mr Putin needs affirmations that it won't join the Western Nato military coalition since he considers any development of it to be a danger to Russia. Nato has dismissed that interest.
Mr Biden said he concurred with a proposition by the Russian government to proceed with tact.
The US president additionally cautioned the American economy could experience the ill effects of interruption to energy supply and value climbs in the possible occasion that assents were collected on Russia in light of any attack of Ukraine.
The American people understand that defending democracy and liberty is never without cost," the US president said. "I will not pretend this will be painless."
He said the administration was working on contingency plans with energy producers and shippers to avert potential supply issues.
Mr Biden warned the proposed Russian Nord Stream 2 natural gas pipeline to Europe "will not happen" if a Ukraine invasion goes ahead.
The US president continued: "To the citizens of Russia: you are not our enemy, and I don't believe you want a bloody, destructive war against Ukraine."
Nato expressed "cautious optimism" on Tuesday about the Russian military's announcement that it had pulled back some of its troops from the border with Ukraine.
US Secretary of State Antony Blinken told his Russian counterpart Sergei Lavrov in a call that the US needed to see "verifiable, credible, meaningful de-escalation".
Earlier, British Prime Minister Boris Johnson tweeted that there were "mixed signals" coming from Russia, because UK intelligence showed Russian field hospitals were being built near the border which could "only be construed as a preparation for an invasion".
Vladimir Putin said before on Tuesday that Russia didn't need war. He talked after a four-hour meeting with German Chancellor Olaf Scholz.
The Russian president told correspondents in Moscow: "Do we need this or not? Obviously, not. For that reason we set forward proposition for a course of exchanges."
Mr Putin likewise said that Nato had up until this point neglected to address Russia's "essential" security concerns. He is requesting that the issue of Ukraine joining Nato be tended to now - even through Ukraine is far from beginning an application to join the coalition.
Mr Scholz said at the joint question and answer session that the development of Russian soldiers was "immense", yet there was as yet an opportunity that conciliatory arrangements could facilitate the pressures.
"I communicated that the troop develop is viewed as a danger," Mr Scholz said at a media instructions. "Obviously we are exceptionally concerned."