The East-West faceoff over Ukraine escalated dramatically Tuesday, with Russian lawmakers authorizing President Vladimir Putin to use military force outside his country and President Joe Biden and European leaders responding by slapping sanctions on Russian oligarchs and banks.

Both leaders signaled that an even bigger confrontation could lie ahead. Putin has yet to unleash the force of the 150,000 troops massed on three sides of Ukraine, while Biden held back on the toughest sanctions that could cause economic turmoil for Russia but said they would go ahead if there is further aggression.

The measures, accompanied by the repositioning of additional U.S. troops to the Baltic nations on NATO’s eastern flank bordering Russia, came as Russian troops rolled into rebel-held areas in eastern Ukraine after Putin said he was recognizing the independence of the separatist region in defiance of U.S. and European demands.

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Speaking at the White House, Biden said the Kremlin had flagrantly violated international law in what he called the “beginning of a Russian invasion of Ukraine.” He warned of more sanctions if Putin went further.

“We are united in our support of Ukraine,” Biden said. “We are united in our opposition to Russian aggression.” When it comes to Putin’s claims about Ukraine’s history and sovereignty, delivered in a wide-ranging, fact-bending speech on Monday, Biden said that “none of us will be fooled.”

Western nations sought to present a united front, with more than two dozen European Union members unanimously agreeing to levy their own initial set of sanctions against Russian officials. Germany also said it was halting the process of certifying the Nord Stream 2 gas pipeline from Russia — a lucrative deal long sought by Moscow but criticized by the U.S. for increasing Europe’s reliance on Russian energy.

The U.S., meanwhile, moved to cut off Russia’s government from Western finance, sanctioning two of its banks and blocking it from trading in its debt on American and European markets.

They included hitting civilian leaders in Russia’s leadership hierarchy and two Russian banks considered especially close to the Kremlin and Russia’s military, with more than $80 billion in assets. That includes freezing all of those bank’s assets under U.S. jurisdictions.

Biden appeared to hold back some of the broadest and toughest of the financial penalties contemplated by the U.S., including sanctions that would reinforce the hold that Germany put on any startup of the Nord Stream 2 pipeline; an export ban that would deny Russia U.S. high-tech for its industries and military; and sweeping bans that could cripple Russia’s ability to do business with the rest of the world.

Biden said he was moving additional U.S. troops to the Baltics. The U.S. is sending about 800 infantry troops and 40 attack aircraft from other locations within Europe, and F-35 strike fighters and AH-64 Apache attack helicopters will shift their locations, according to a defense official.

Earlier Tuesday, members of Russia’s upper house, the Federation Council, voted unanimously to allow Putin to use military force outside the country — effectively formalizing a Russian military deployment to the rebel regions, where an eight-year conflict has killed nearly 14,000 people.

Shortly afterward, Putin laid out three conditions to end the crisis that has threatened to plunge Europe back into war, raising the specter of massive casualties, energy shortages across the continent and global economic chaos.

Putin said the crisis could be resolved if Kyiv recognizes Russia’s sovereignty over Crimea, the Black Sea peninsula that Moscow annexed from Ukraine in 2014, renounces its bid to join NATO and partially demilitarizes. The West has decried the annexation of Crimea as a violation of international law and has previously flatly rejected permanently barring Ukraine from NATO.

Asked whether he has sent any Russian troops into Ukraine and how far they could go, Putin responded: “I haven’t said that the troops will go there right now.” He added that “it’s impossible to forecast a specific pattern of action –- it will depend on a concrete situation as it takes shape on the ground.”

The EU announced initial sanctions aimed at the 351 Russian lawmakers who voted for recognizing separatist regions in Ukraine, as well as 27 other Russian officials and institutions from the defense and banking sectors. They also sought to limit Moscow’s access to EU capital and financial markets.

With tensions rising and a broader conflict looking more likely, the White House began referring to the Russian deployments in the region known as the Donbas as an “invasion” after initially hesitating to use the term — a red line that Biden had said would result in severe sanctions.

“We think this is, yes, the beginning of an invasion, Russia’s latest invasion into Ukraine,” said Jon Finer, principal deputy national security adviser, said on CNN. “An invasion is an invasion, and that is what is underway.”

The White House announced limited sanctions targeting the rebel-region Monday evening soon after Putin said he was sending troops to eastern Ukraine. A senior Biden administration official, who briefed reporters about the sanctions targeting the breakaway region noted “that Russia has occupied these regions since 2014” and that “Russian troops moving into Donbas would not itself be a new step.”

Biden on Tuesday described the repositioning of U.S. forces as “totally defensive moves on our part” and said the U.S. had no plans to deploy its forces in Ukraine. The organization’s mutual-defense pact considers an attack on one member to be an attack against all.

Western leaders have long warned Moscow would look for cover to invade — and just such a pretext appeared to come Monday, when Putin recognized as independent two separatist regions in eastern Ukraine, where government troops have fought Russia-backed rebels. The Kremlin then raised the stakes further by saying that recognition extends even to the large parts now held by Ukrainian forces.

Putin said Russia has recognized the rebel regions’ independence in the borders that existed when they made their declaration in 2014 — broad territories that extend far beyond the areas now under separatist control and that include the major Azov Sea port of Mariupol. He added, however, that the rebels should eventually negotiate with Ukraine.

Condemnation from around the world was quick. Ukrainian President Volodymyr Zelenskyy said he would consider breaking diplomatic ties with Russia and Kyiv recalled its ambassador in Moscow.

If Putin pushes further into Ukraine, NATO chief Jens Stoltenberg insisted the West would move in lockstep. “If Russia decides once again to use force against Ukraine, there will be even stronger sanctions, even a higher price to pay,” he said.

British Prime Minister Boris Johnson said the U.K. would slap sanctions on five Russian banks and three wealthy individuals. He warned a full-scale offensive would bring “further powerful sanctions.”

Zelenskyy said he was calling up some of the country’s military reservists but added there was no need for a full military mobilization.

In an address to the nation, Zelenskyy said his decree applied only to those assigned to the so-called operational reserve, which is typically activated during ongoing hostilities, and covers “a special period of time,” without clarifying what that means.

“Today there is no need for a full mobilization. We need to quickly add additional staff to the Ukrainian army and other military formations,” he said. National Security and Defense Council Oleksii Danilov said earlier this year that Ukraine can call up to 2.5 million people.

Russia has long denied it has any plans to invade Ukraine, instead blaming the U.S. and its allies for the crisis and describing Ukraine’s bid to join NATO as an existential challenge to Russia. Putin reiterated those accusations in an hourlong televised speech on Monday, when he announced that Russia would recognize the rebels.

“Ukraine’s membership in NATO poses a direct threat to Russia’s security,” he said.