Ukrainian President Petro Poroshenko convened his generals Tuesday to discuss the latest failed bid to negotiate an end to clashes with pro-Russian rebels that saw seven troops killed in another wave of attacks.

Ukrainian President Petro Poroshenko convened his generals Tuesday to discuss the latest failed bid to negotiate an end to clashes with pro-Russian rebels that saw seven troops killed in another wave of attacks.

Poroshenko has found himself trapped between more militant Ukrainian nationalists and Western leaders who hope to see an end to 16 months of fighting in the European Union's backyard.

The pro-EU leader sent his personal envoy to the Belarussian capital Minsk on Monday to discuss a new weapons withdrawal agreement with rebel and Moscow negotiators.

But the European-mediated talks fell apart after more than six hours due to what one rebel said was Kiev's refusal to pull back its forces from four strategic sites.

"We need to clearly determine a plan for strengthening our defenses in case of the conflict's escalation," the presidency quoted Poroshenko as telling members of Ukraine's powerful National Security and Defense Council and top ministers.

Council Secretary Oleksandr Turchynov reported the death of three more soldiers in overnight rocket attacks. Kiev said four of its troops had been killed on Monday and the rebels reported one loss in the past two days.

The Ukrainian government and its Western allies fear that the war -- which has already killed nearly 7,000 people -- may turn into a "frozen conflict" in which low-level violence becomes a constant menace that leaves much of eastern Europe on a permanent state of alert.