President Petro Poroshenko on Monday ordered Ukraine’s army to regain control of the country’s porous border with Russia within a week, adding that once that goal is achieved, he would offer a temporary cease-fire in the fighting with separatist rebels.

Speaking at a meeting with his security team, Poroshenko said government troops have already reestablished control of about 150 miles of the border. That includes some of the border points seeing the greatest infiltration of fighters and equipment from Russia, he said, although he did not specify how much of the more than 1,200-mile-long border remains under rebel control.

Poroshenko said that a cease-fire would be the first step toward resolving the conflict that has raged in the east since April.

“We don’t need talks for the sake of talks,” he said.

It remains unclear whether the rebels would respond favorably to a call by Poroshenko to stop fighting — or whether the military can carry out his ambitious instructions.

Against the backdrop of fighting in Odessa and Slovyansk, Ukraine President Petro Poroshenko calls for a truce in eastern Ukraine. (Reuters)

Poroshenko proposed a truce in his inaugural address when he assumed office on June 7, but rebels rebuffed that call.

Ukraine’s military, which has been weakened during two decades of neglect and budget cuts, has struggled to contain the recent insurgency.

Andriy Parubiy, head of Ukraine’s National Security and Defense Council, declined to specify when the military might complete the operation in the east.

“I can only say that the president of Ukraine has ordered a prompt solution of these tasks,” he said, according to the Ukrainian Interfax news agency.

Parubiy estimated that 15,000 to 20,000 “armed terrorists” are in the Donetsk and Luhansk regions, home to the most intense separatist sentiment and fighting.

He also said that a significant force of well-equipped soldiers has been redeployed close to territories bordering Ukraine in the past day or two. The force’s assets include personnel and transport planes used by the Russian air assault division, he said.

Even as Poroshenko was proposing a cease-fire, separatists in the eastern city of Donetsk were expanding their footprint. Gunmen took over several buildings in the city, including the offices of the regional treasury, the national bank, the tax administration and a private energy firm owned by billionaire Rinat Akhmetov, according to regional Ukrainian officials.

Serhiy Taruta, the governor of Donetsk, said the takeover of the regional treasury means that the state may stop paying salaries and pensions.

The Organization for Security and Cooperation in Europe said as many as 4 million people in the Donetsk region risk losing water because the pumping station and pipeline there have been damaged in fighting between government troops and pro-Russian separatists.

The organization said city crews had started making repairs but stopped because of gunfire nearby. Konstantin Batozsky, an adviser to Taruta, said the water cutoff may be only a few days away.

Meanwhile, Russia’s Foreign Ministry sent a note to Ukraine demanding that protesters who damaged the Russian Embassy in Kiev be prosecuted.

The note accused Kiev authorities of not stepping in to stop the protesters, who on Saturday night pelted the embassy with eggs, bricks and paint, breaking every window, and overturned embassy vehicles. A crowd of several hundred people went to the embassy after learning pro-Russian separatists had shot down a Ukrainian military plane, killing all 49 aboard. Barriers are now up at the embassy, preventing protesters from gathering on the sidewalk in front of the building.

In the note, Russian Foreign Minister Sergei Lavrov said the protesters “wanted to see blood.”