WASHINGTON — US President Joe Biden has said he thinks his Russian counterpart Vladimir Putin will "move in" on Ukraine, but does not want "full-blown war".

"My guess is he will move in, he has to do something," Biden said, but he warned that the Russian leader would pay a "serious and dear price" for "testing" the West.

Biden, speaking at a news conference to mark his one-year anniversary in office, also said a “minor incursion” by Russia would elicit a lesser response. He later sought to clarify that he was referring to a non-military action, such as a cyberattack, that would be met with a similar reciprocal response, and that if Russian forces cross the Ukrainian border, killing Ukrainian fighters, “that changes everything.”

But the comments also hinted at the challenge of keeping the United States and its NATO allies united in their response to Russia.

Biden, during the nearly two-hour press conference, indicated there was disagreement within NATO about imposing strong sanctions on Russia because it would harm the economies of some European allies.

In explaining the minor incursion remark, he said “it’s very important that we keep everyone in NATO on the same page.”

The news conference came at a critical moment in Europe as Russia has amassed 100,000 troops near the Ukrainian border and a series of talks in Europe last week failed to ease tensions.

Secretary of State Antony Blinken will meet with Russian Foreign Minister Sergey Lavrov in Geneva on Friday. On Wednesday, Blinken met with Ukraine’s president in Kyiv and he heads to Berlin on Thursday for talks with allies.

Biden reiterated that he did not think that Putin has made a final decision on whether to invade, but speculated "my guess is he will move in."

Even after he sought to clarify his comments about a potential NATO response to a “minor incursion” by Russia, the White House moved quickly to make clear that Biden was not indicating to Putin that the US would tolerate some military action against Ukraine.

White House press secretary Jen Psaki noted that the Russians could turn to an “extensive playbook of aggression short of military action, including cyberattacks and paramilitary tactics.”

“President Biden has been clear with the Russian President: If any Russian military forces move across the Ukrainian border, that’s a renewed invasion, and it will be met with a swift, severe, and united response from the United States and our Allies,” Psaki said in a statement.

As the White House did cleanup, Biden faced a barrage of criticism over the “minor incursion” remark.

“This is the wrong way to view this threat," said Sen. Rob Portman, R-Ohio, who was part of a bipartisan congressional delegation that traveled to Kyiv over the weekend to meet with Ukrainian officials. "Any incursion by the Russian military into Ukraine should be viewed as a major incursion because it will destabilise Ukraine and freedom-loving countries in Eastern Europe.”

Sen. Ben Sasse, R-Neb., said Biden effectively “gave Putin a green light to invade Ukraine by yammering about the supposed insignificance of a ‘minor incursion.’”

“He projected weakness, not strength,” Sasse said.

If Russia invades, Biden said, one action under consideration was limiting Russian transactions in US financial institutions, including “anything that involves dollar denominations."

Biden was referring to potentially limiting Russia's access to “dollar clearing” — the conversion of payments by banks on behalf of clients into US dollars from rubles or other foreign currency, according to a senior administration official who was not authorised to comment publicly.

The US president said he believes the decision will “solely” be Putin's and suggested he was not fully confident that the Russian officials with whom top White House advisers have been negotiating are fully informed about Putin's thinking.

“There’s a question of whether the people they’re talking to know what he’s going to do,” Biden said.

Ukraine, meanwhile, said it was prepared for the worst and would survive whatever difficulties come its way. The president urged the country not to panic.

Russian military activity has been increasing in recent weeks, but the US has not concluded whether Putin plans to invade or whether the show of force is intended to squeeze the security concessions without an actual conflict.

In Kyiv, Blinken reiterated Washington's demands for Russia to de-escalate the situation by removing its forces from the border area, something that Moscow has flatly refused to do. And, Blinken said he wouldn't give Russia the written response it expects to its security demands when he and Lavrov meet in Geneva.

Meanwhile, a top Russian diplomat said Moscow would not back down from its insistence that the US formally ban Ukraine from ever joining NATO and reduce its and the alliance's military presence in Eastern Europe.

Deputy Foreign Minister Sergei Ryabkov said Moscow had no intention of invading Ukraine but that its demands for security guarantees were non-negotiable.

The US and its allies have said the Russian demands are non-starters, that Russia knows they are and that Putin is using them in part to create a pretext for invading Ukraine, which has strong ethnic and historical ties to Russia. The former Soviet republic aspires to join the alliance, though has little hope of doing so in the foreseeable future. — Agencies