The Russians are coming, the Russians are coming — to eastern Ukraine, or at least their humanitarian aid is on its way. Ukraine and the West objected when Russia first proposed to send hundreds of trucks across the border into Luhansk and other combat zones during a momentary pause in the fighting. Russian television showed the fleet of shiny, white, and innocuous-looking trucks being loaded with food and other goods while diplomats fought over what Moscow’s true intentions are with this move.

What exactly are the words to “Convoy” in Russian anyway, tovarisch?

Earlier today, Ukraine refused to allow any of the trucks to enter, worried about a Russian pretext for war. Later, though, Ukrainian officials agreed to the transmission of aid — but only under strict conditions, which the Russians have not yet met:

A convoy of 280 Russian trucks reportedly packed with aid headed for eastern Ukraine on Tuesday, but Kiev said it would only allow the goods through under the close supervision of the international Red Cross.

A Ukrainian security spokesman said the convoy of vehicles was being managed by the Russian army and that it could not be allowed into the country.

The humanitarian crisis provoked by fighting between government troops and pro-Russian separatist militants in eastern Ukraine has reached a critical point in recent days and heightened the urgent need for intervention.

But Ukraine and the West have voiced concerns that Russia could use the aid initiative as a cover for sending troops into separatist-held territory.

“This convoy is not a certified convoy. It is not certified by the International Committee of the Red Cross,” said Andriy Lysenko, a spokesman for Ukraine’s National Security and Defense Council. “No military structures have the right to escort humanitarian aid convoys, especially into another state.”

The Red Cross has no idea what’s in the trucks. Russia did not involve them in the project, and the ICRC did not have the opportunity to inspect the cargo holds of the vehicles. Ukraine, which also insists that the aid has to come through a border checkpoint controlled by Kyiv — preferably as far away from the fighting as possible — said any attempt to bring the vehicles into Ukraine without government approval would be considered an attack:

“This cargo will be reloaded onto other transport vehicles (at the border) by the Red Cross,” Ukrainian presidential aide Valery Chaly said.

“We will not allow any escort by the emergencies ministry of Russia or by the military (onto Ukrainian territory). Everything will be under the control of the Ukrainian side,” he told journalists. …

The U.S., French and Australian governments voiced concern that Russia, sole international supporter of rebels in Ukraine’s Russian-speaking east, could use the humanitarian deliveries to carry out a covert operation to help fighters who appear to be on the verge of defeat.

With Ukraine reporting Russia has massed 45,000 troops on its border, NATO said on Monday that there was a “high probability” Moscow might now intervene militarily in Ukraine.

The Washington Post editorial board urged the Obama administration and the EU to have another set of sanctions at the ready if Vladimir Putin’s convoy breaches the Ukrainian border:

RUSSIA AGAIN appeared on the verge of invading Ukraine over the weekend, this time in the guise of a “humanitarian operation.” President Obama and other Western leaders sounded the alarm, warning that the prospective intervention “is unacceptable, violates international law and will provoke additional consequences,” as a White House statement put it. For his part, Ukrainian President Petro Poroshenko agreed to a non-military relief operation under the auspices of the Red Cross that would allow for Russia’s participation.

Whether that would be enough to deter Russian ruler Vladi­mir Putin wasn’t clear on Monday. According to NATO Secretary General Anders Fogh Rasmussen, tens of thousands of Russian troops remained poised on Ukraine’s border; he said “there is a high probability” of invasion. Though a vacationing President Obama is already overseeing U.S. air strikes in Iraq, the United States and its allies must be prepared to act quickly if Russian military forces cross the frontier. …

Mr. Poroshenko is still offering a peace plan that involves a cease-fire and political dialogue on the condition that Ukraine’s border is sealed to further infiltrations of Russian weapons and fighters. That could perhaps provide a face-saving exit for Mr. Putin, but it’s one Moscow is unlikely to embrace unless its proxy forces are on the verge of defeat. That’s why the Ukrainian military operation should continue with Western support, including fresh aid for the army, and why the United States and its allies should do everything possible to deter Mr. Putin’s “humanitarian” invasion. What “additional consequences” can Moscow expect if it crosses the line? A robust package should be readied and telegraphed to the Kremlin.

The convoy doesn’t even have to include military supplies to produce the kind of provocation Putin has clearly desired for months. They can set themselves up as “observers” once inside Ukraine and block Kyiv from further military action against the rebels. If the Ukrainian military does proceed, then Putin can send in his troops in order to protect his “humanitarian” mission.

Whatever happens, it’s going to happen quickly. The West had better be prepared to shut Russia down economically when it does — and it would be best to “telegraph” that intention to Putin now, as the WaPo’s editors advise, in order to avoid the situation altogether. If Putin wants to donate aid, let him work through the Red Cross. Anything else is a thinly-veiled provocation for a European war that only the Russian media would miss.