On Friday, the two world leaders with the most power — and the most responsibility — to respond to Russian provocations in Ukraine held a joint press conference, and they gave Vladimir Putin some reason for concern. If, that is, Putin calculates that they really mean it.

US President Barack Obama (L) and German Chancellor Angela Merkel walk back to the Oval Office in the White House after giving a press conference following their meeting on May 2, 2014 in Washington. Obama welcomed Merkel at the White House for discussions on the escalating crisis in Ukraine, her first visit to Washington since revelations that the US may have tapped her mobile phone. AFP PHOTO/Jewel SamadJEWEL SAMAD/AFP/Getty Images President Obama and German Chancellor Angela Merkel walk back to the Oval Office after giving a press conference following their meeting on May 2, 2014. JEWEL SAMAD/AFP

President Obama and German Chancellor Angela Merkel set a new red-line for Putin, insisting that Ukraine’s planned presidential elections must go forward on May 25. If Russian-backed separatists in eastern Ukraine — or a more formal Russian invasion — upset the polling, Russia will face a new round of economic sanctions, and ones that are presumably much tougher. The West, Obama and Merkel said, would finally begin targeting whole sectors of the Russian economy, not just a few Putin cronies. Obama did not announce specific measures, but he said that experts were considering restrictions on the Russian energy, arms and finance sectors. Both east-west trade and “lines of credit,” the president warned, would be at risk.

It is true that Ukraine figures more prominently in Russian minds than in those of the West. Russian leaders may well be willing to risk more to influence the direction in which the country, or a large swath of the country, orients. But there is also an asymmetry in economic leverage that works in the West’s favor. Russia probably needs the Western financial system more than the Western financial system needs Russia. The picture is not quite as simple on energy, because Europe depends so heavily on Russian gas. But Russia, likewise, depends on European customers to prop up its economy.

There are at least two reasons Putin may not shy from the West’s new red-line. If he takes Obama and Merkel’s threat seriously, he might still figure that Russia is willing to endure much more economic hardship to maintain and expand Russian influence along its borders, in which case Europe must recognize a long-term, dangerous threat in Putin’s Russia. Additionally or alternatively, Putin may not take Obama and Merkel seriously, betting that the West is unlikely to make good on its threat of truly punishing sanctions. Obama’s waffling on previous red-lines might factor into this sort of calculation. But more important is that many in Europe still appear unwilling to sacrifice much in the Ukraine crisis.

Earlier this week, a group of European business leaders flew through Washington arguing, among other things, that tougher, sectoral sanctions are a bad idea. The United States should have a serious contingency plan in place if these voices prevail on the continent. But it also should not have to. Russia has insulted sovereignty, order and peace in Europe, and Angela Merkel, Europe’s most influential head of government, has now put her credibility on the line. Ukrainians in Kiev, Odessa, L’viv and Donetsk will be watching to see if she lives up to the literal meaning and the implied spirit of her words. So will we in the rest of the world.