Ukrainian President Petro Poroshenko in February. (Valentyn Ogirenko/Reuters)

NEARLY SIX months after Russia agreed to an immediate cease-fire in eastern Ukraine, its forces continue to shell and rocket Ukrainian positions on a daily basis. Far from pulling back heavy weapons or withdrawing its troops as required by the agreement, it has built military bases and deployed 9,000 troops inside Ukraine and stationed another 50,000 just outside the border, according to Ukrainian and NATO officials. Ukraine’s national security council warned last month that Moscow had completed preparations for a new offensive in three different directions from the territory it currently controls.

How are Western governments responding to this aggression? Last month the Obama administration slightly tightened existing sanctions on Russia, and the Pentagon announced that training of Ukrainian special forces would be extended to regular army units. Mostly, however, the United States has joined with France and Germany in applying heavy political pressure — on the government of Ukraine.

Since a meeting in May between Secretary of State John F. Kerry and Russian President Vladi­mir Putin, U.S. officials have been leaning on the democratically elected and pro-Western administration of Petro Poroshenko to adopt constitutional changes and authorize elections that would legitimize the authorities Russia installed in eastern Ukraine and grant the areas they occupy a special legal status. Last month Ukraine’s parliament reluctantly gave preliminary approval to the changes after Mr. Poroshenko warned lawmakers Ukraine would have to face Russia without allies if it did not adopt them.

The political formula was imposed by Russia as part of what is known as the “Minsk 2” agreement in February. Germany, France and Ukraine agreed to the deal in a desperate effort to stop an escalating military conflict. The shooting diminished, but never stopped; Russia and its proxies have never respected the cease-fire. Yet now the German and French governments have enlisted the help of the Obama administration in seeking unilateral Ukrainian compliance with Minsk 2’s onerous political terms, which if fully implemented would implant a Russian-controlled entity inside Ukraine’s political system.

U.S. officials say Ukrainian steps toward compliance put pressure on Russia and deprive it of a pretext for launching another full-scale military offensive. But Moscow’s aggressive propaganda apparatus relentlessly portrays Ukraine as violating the deal; and Mr. Putin hasn’t needed a legitimate pretext for his previous aggressions. Even if Russia respected the cease-fire, the terms it seeks for reincorporating the areas it holds into Ukraine would cripple the country’s democracy and independence — which is Mr. Putin’s goal.

Rather than legitimize Russia’s puppet entity, Ukraine would be better off leaving it isolated and forcing Moscow to sustain it, as it does similar enclaves in Georgia and Moldova. The Obama administration, for its part, ought to be doing more to bolster Ukraine’s defenses, so that Russia will be deterred from the offensive it is threatening — and it should tell European allies that the political solution they are trying to force is unworkable as well as wrong.