Just when the news out of Eastern Ukraine couldn’t get any worse, it did. Separatists controlling the area of the MH17 wreckage have declared that they can only ensure international investigators will have access to the crash site if Ukraine agrees to a truce: “We declare that we will guarantee the safety of international experts on the scene as soon as Kiev concludes a ceasefire agreement," said Andre Purgin, a senior leader of the self-declared Donetsk People’s Republic. The declaration amounts to blackmail, as Nina Ivanovna put it. The separatists are holding the bodies of MH17 passengers hostage in exchange for territory.

It appears that the bodies are in fact being held hostage on board refrigerated train cars bound for an undisclosed location, BBC reports. The vicinity around MH17 remains unsecured, the black boxes are likely in the hands of rebels, and experts arriving at the scene have been greeted with gunfire. For the past few days, shelling has continued in the area around the crash site as the Ukrainian army has pressed forward with its anti-terrorist operation. In Kiev, the incident has radicalized politics: “‘peace talks’ have become a toxic term for Ukrainian politicians. Kiev's political class wants to win this war on the battlefield, not at the negotiating table,” Maxim Eristavi reports.

The leaders of Ukraine, Russia, and the U.S. have called for a ceasefire that could play into the hands of the separatists, affording them time to cover their tracks and consolidate forces; that's why the rebels are calling for a truce. In remarks on Thursday in response to the news of MH17, both President Barack Obama and President Vladimir Putin called for an immediate ceasefire in Eastern Ukraine. Ukrainian President Petro Poroshenko did the same on Friday on the phone with Vice President Joe Biden.

The aim of a new ceasefire would be to make sure peripheral fighting does not impact the site of the wreckage and that international investigators can safely get to Donetsk, and to stop clashes that continue to claim lives in the east. All are unquestionably imperative measures to achieve, but declaring a ceasefire is unlikely to do so.

Ceasefires have already failed Ukraine twice in the last two months. They both lasted ten days, and both allowed the rebels to consolidate forces and ready for the confrontations to come. Both took place under the condition that the Ukraine-Russia border is sealed, a nearly impossible feat given the time frame, so the flow of arms and fighters from Russia to Ukraine remained open. Moreover, neither ceasefire was actually a ceasefire: sporadic fighting continued in the east, and fighters on both sides were killed. Factionalism between separatist forces meant that it was impossible to get all fighters to adhere to the terms of the agreements. Given all that, it’s understandable why there is little appetite in Kiev for a break in the fighting, and why the government is resolutely unwilling to negotiate with separatists: They already tried that, twice. Even when the first one was imposed, at the end of June, part of the goal was to “create a political justification for them to say, ‘We tried, now we’ll use force,’” Eugene Rumer, director of the Carnegie Endowment’s Russia and Eurasia program, told me at the time.