DONETSK, Ukraine — Defiant pro-Russian militants in eastern Ukraine pushed this country to the brink of war or dissolution Monday, expanding their hold while the acting president failed to make headway in trying to end the crisis.
After an ultimatum to the militants was ignored, the acting president, Oleksandr Turchynov, first vowed to rout them by force, then held out the offer of a referendum to decide Ukraine's fate, then proposed a peacekeeping intervention by the United Nations.
Nothing he said moved the pro-Russian forces, who seized another police station in another town, Horlivka.
In a nation of 44 million, it became clear that a few hundred men, operating on the eastern fringes of the country with guns and unmarked uniforms, have brought Ukraine to a deeply dangerous juncture.
The mood was tense in this industrial city of nearly 1 million, where many residents were staying inside after dark. Turchynov and other Ukrainian officials are sure that Russia is guiding the militants as they have steadily taken over one government building after another. They have vocal support on that score from Washington and London. Russia denies it, and the Russian foreign minister, Sergey Lavrov, said Monday it is the West's responsibility to rein in the government in Kiev so that there are no violent attacks on the militants.
The crisis, which began to the south, in Crimea, is now focused on militants who say they represent the "People's Republic of Donetsk," an eastern region. It has brought relations between Russia and the West to their lowest point at least since the Soviet invasion of Afghanistan in 1979.
"There can't really be any real doubt that this is something that has been planned and brought about by Russia," British Foreign Secretary William Hague said as he arrived in Luxembourg to meet with his European counterparts.
In Moscow, a spokesman for Vladimir Putin said the Russian president has been watching the crisis with "great concern" and had received "many appeals, addressed personally to Putin, asking to help in this or that way and asking to intervene in this or that way."
Officials at the Pentagon on Monday protested what they described as a provocative flyover by a Russian attack aircraft that flew at close range for 90 minutes over a U.S. Navy ship that had been sent into the Black Sea.
The anonymous appeal for help has been a favorite tactic of Russian interventionists for the better part of a century. It was also a feature of Russia's involvement in Crimea in late February and March before that region's annexation by Moscow.
As the evening wore on there was still no sign of Turchynov's promised attack on separatist positions in eastern Ukraine by forces loyal to Kiev. Turchynov and other officials had said that if no resolution was reached by 8 a.m. Monday, an "antiterrorist" operation would begin.
In the heart of Donetsk, a group of pro-Russians occupying the city's Lenin Square said they were convinced that the Kiev government would not carry out its threat to deploy the Ukrainian army in the region. Unlike some activists, they said they did not want the Russian military to roll into the region. They were holding out for a referendum on the region's future.
On Monday, Turchynov unexpectedly held out the offer of a referendum to determine the amount of power-sharing between Kiev and the regions. The separatists have been saying that a referendum is their principal goal, but many were quick to dismiss Turchynov's proposal as insincere — as was the Russian Foreign Ministry.
Turchynov also talked with U.N. Secretary-General Ban Ki Moon and later suggested that a U.N. peacekeeping force could enter eastern Ukraine. But the almost-certain opposition of Moscow, standing up for the men with guns, makes that problematic.