In an interview with Euronews, the US Secretary of State says Moscow must understand that attacking Ukraine would not be in Russia's interests.
The United States issued a strong warning to Russia on Thursday, calling for it to stay away from Ukraine.
US Secretary of State Antony Blinken held talks with Russian Foreign Minister Sergei Lavrov at an OSCE meeting in Stockholm where he warned of "serious consequences" if Moscow decided to pursue confrontation.
Ukrainian and Western officials are worried that a Russian troop buildup near Ukraine could herald an invasion.
“We don't know President Putin's intent. We don't know if he's made a decision to take renewed, aggressive action against Ukraine, but what we do know is that he's putting in place the capacity to do so and to do so on on short, on short notice," Blinken told Euronews after his meeting, adding that concern was widespread among European partners.
"What's most important for Russia to understand is that actions have have consequences. Those consequences are real. They're not in Russia's interests, and having a conflict is in no one's interest," he went on.
President Biden, said Blinken, had told President Putin that the US wanted a "stable, predictable relationship with Russia", but if Moscow moved "aggressively again against Ukraine" this would be moving in "exactly the opposite direction".
"I don't think that's good for for any of us, but president was equally clear if Russia chooses to act recklessly, we'll respond."
Pressed on what such action might involve given that sanctions were already in place, Blinken declined to be specific, but said "many things" were being considered that would have "a very high impact, and are things that we have not done in the past that we've refrained from doing".
Addressing the OSCE meeting earlier, Blinken urged Russia "to respect Ukraine's sovereignty and territorial integrity to de-escalate, reverse the recent troop buildup, return forces to normal peaceful positions, and to implement the Minsk commitments."
But Moscow has insisted it has no intention of attacking Ukraine, accusing Kyiv and its Western backers of making up the claims to cover up their own allegedly aggressive designs.
"I have no doubts that the only exit from the current crisis (in relations), and it really is quite tense, is to find a balance of interests," Lavrov said, as he met Blinken on the sidelines of a ministerial meeting of the Organization for Security and Cooperation in Europe in the Swedish capital.
"Regarding the rise in tensions in Europe that everyone is talking about, in part along the border of Russia and Ukraine, you know our position on this well. As President Putin underlined, we do not want any conflicts."
Vladimir Putin has warned NATO against deploying its troops and weapons to Ukraine, saying it represents a red line for Russia and would trigger a strong response.
He said Wednesday that Moscow would seek Western guarantees precluding any further NATO expansion and deployment of its weapons near Russia's borders.
The 2015 Minsk deal included an OSCE-monitored cease-fire, a pullback of heavy weapons and foreign fighters from the line of contact and an exchange of prisoners of war. It also envisaged granting broad autonomy to the separatist regions and a sweeping amnesty for the rebels in a diplomatic coup for Russia.
The agreement stipulated that Ukraine could only regain control over the border with Russia in rebel regions only after they receive a broad autonomy and hold elections, a provision also resented by many in Ukraine.
The agreement helped end large-scale battles, but frequent skirmishes have continued, and a political settlement has failed while Moscow and Kyiv have traded blame.
Moscow argues it's not a party to the deal between Ukraine and self-proclaimed separatist regions and denies Ukrainian and Western assertions of sending its troops and weapons into eastern Ukraine.