US President Barack Obama's threats of "costs" did not sway Vladimir Putin's calculations on Crimea.
Now he must see if the pain he plans to escalate on Russia will be sufficiently acute to do any better.
The White House's initial strategy of seeking to defuse the crisis, offering Russia an "off-ramp" and warning of consequences has run its unsuccessful course.
Putin's swift absorbtion of Crimea and his fiery speech Tuesday, which seemed to put a full stop on the post-Cold War era, forced the Obama administration into a new phase.
The plan now is to hike up the economic cost to Moscow and punish its move into the Ukrainian region by deepening its isolation.
Read: Welcome to Republic of Crimea, the world's newest statelet
Crimea's 6 steps towards joining Russia after Soviet-style vote
Crimea annexation: In Putin vs West, India can't pick a side
A man plays accordion as people dance during celebrations in Sevastopol on March 17, 2014. AFP PHOTO
Washington must also try to keep the crisis from careening dangerously out of control -- all while bolstering new allies in post-Soviet Europe and firming the West's resolve.
In the longer term, the White House faces an uncomfortable self-examination of how it got here. Yet another US look at how to handle President Putin is in order.
The strategic implications meanwhile of the worst East-West crisis since the Cold War threaten to consume much of the political bandwidth of Obama's remaining second term.
Sanctions with teeth?
Ukrainian interim forces recruits stand guard in front of weapons during a training session not far from Kiev on March 17, 2014. AFP PHOTO
Obama will head to Europe next week on a trip which is suddenly the most important by a US president in many years.
He called G7 leaders to meet him in The Hague and will try to lock in Russia's isolation and convince European states to build a sanctions regime with teeth.
"We can calibrate our response based on whether Russia chooses to escalate or to de-escalate the situation," Obama said Monday.
Washington sanctioned 11 officials, including members of Putin's inner political circle, on Monday, drawing only sneers from Moscow.
Read: Crimea annexation: In Putin vs West, India can't pick a side
Defiant Putin signs treaty to annex Crimea, Ukraine tense
Women present their bags to armed men in riot gear, performing identity and hand bag checks on people walking near the building of Crimea's regional parliament in Simferopol, Ukraine, Monday, March 17, 2014. AP
But the White House promises more to come.
Its economic leverage however over Moscow is finite, despite a widening trade relationship which has seen US firms such as Boeing and Exxon Mobil become players in the Russian market.
Europe, with its huge trade and energy relationships with Moscow, holds the key.
"The Europeans are in a better position to do damage to the Russian economy," said Anton Fedyashin, a Russia expert at American University.
But will European leaders, for all their tough talk, follow through with measures that will also inflict a cost on their own fragile economies?
"I seriously doubt that most European countries are going to say, 'Yes, we are ready to support that plan,'" Fedyashin said.
So far, Washington has targeted individuals and not the wider Russian economy. But it has hinted politically powerful tycoons should beware.
Longer term, it must decide whether to attempt the kind of banking sanctions which humbled Iran's economy.
Even if it does not, US officials hope that keeping such a threat on the table could dampen Russian economic confidence and force Putin's hand.
"I wouldn't, if I were you, invest in Russian equities right now -- unless you are going short," said White House spokesman Jay Carney.
People hold their Ukrainian national flags and a poster featuring Russian President Vladimir Putin and reading "Stop Putin" as they demonstrate in front of the Russian Ambassy in Berlin on March 17, 2014. AFP PHOTO
Russia's incursion into Crimea and the fear of a move further into eastern Ukraine sent a Cold War chill through Europe.
It prompted US Vice President Joe Biden to slip behind the old Iron Curtain with an unequivocal strategic message.
"I want to make it unmistakingly clear to you and to all our allies in the region that our commitment to mutual self-defense under Article 5 of NATO remains iron-clad," Biden told Polish President Bronislaw Komorowski on Tuesday.
Obama will pick up the banner next week and Washington has already sent six extra F-15 fighters to step up NATO air patrols over the Baltic.
The Crimea crisis may also bring NATO, which has struggled to define a post-Cold War role, back to its geostrategic roots. Tough questions are pending about sinking European defense budgets and Obama's own plans to trim Pentagon accounts.
The president's political foes are calling on him to revive plans to station US missile defense interceptors in Poland and the Czech Republic.
But a senior US official effectively scotched the idea, saying missile defense "has never been about Russia."
Obama has repeatedly asked Congress to pass $1 billion in loan guarantees for Ukraine.
But officials have been coy on reported Ukrainian requests for military aid to avoid provoking the Kremlin.
Obama will also next week urge allies to do more to help Ukraine navigate an economic crisis exacerbated by the loss of a huge loan from Russia.
The International Monetary Fund and the World Bank will be at the forefront -- but the bill is not cheap: Ukraine needs 25 billion euros over two years.
Even as he cranks up the heat on Putin, Obama will seek to cool military tensions between two powers which control 90 percent of the world's nuclear arms.
A move into eastern Ukraine "would be as egregious as any step that I can think of," Secretary of State John Kerry said in a clear warning to Moscow.
Such a scenario would "require a response that is commensurate with the level of that challenge."
But can anyone really know how seriously Putin now takes American threats?\
Watch video: Putin signs treaty with Crimean leaders on Ukrainian Black Sea peninsula