Ukraine's prime minister, Arseniy Yatsenyuk, says building an army strong enough to stop Russian aggression is the country's number one task.
NATO and European observers report seeing Russian tanks, troops and weapons crossing the border into eastern Ukraine this past week. A cease-fire declared in September has been violated consistently almost since the day it was signed.
Ukrainian President Petro Poroshenko said the situation in the east must be resolved through dialogue with the Russian-backed separatists. However, Poroshenko said Friday the Ukrainian military is "willing and able to fight back" if the cease-fire collapses completely.
Russian President Vladimir Putin has said he wants to reach a compromise with Ukraine, but the Kremlin denies having any soldiers or weapons in rebel-controlled areas.
Moscow also says it is Ukraine that is massing forces along the front lines, ignoring an agreement to pull them back.
U.S. Secretary of State John Kerry has called for the immediate implementation of the cease-fire and securing and monitoring of the Ukraine-Russia border.
A State Department spokesman said Kerry spoke with Russian Foreign Minister Sergei Lavrov Friday, expressing grave concern over increased Russian support for the separatists.
Meanwhile, as world leaders gathered in Australia for a summit of the Group of 20 economic powers, Russian President Vladimir Putin, in an interview Friday with Russia's official Tass news agency, complained about U.S.-led sanctions against Russia for its military activity in Ukraine. He said Washington is "crudely violating" the spirit of international cooperation.
European Union President Herman von Rompuy says European foreign ministers will meet Monday after the summit to assess the situation in Ukraine and talk about "possible further steps," which could mean more sanctions against Moscow.
EU leaders also plan to discuss Ukraine with U.S. President Barack Obama on the sidelines of the summit.
Russia makes move
NATO and European observers this week reported the movement of troops, tanks and artillery from Russia into eastern Ukraine. The Kremlin denies having any soldiers or weapons in rebel-controlled areas. Moscow also says it is Ukraine that is massing forces along the front lines, ignoring an agreement to pull them back.
The Reuters news agency Friday quoted Western officials as saying that rebel forces had fired on and jammed unmanned drone reconnaissance aircraft deployed by Organization for Security and Cooperation in Europe monitors days before the armed convoys were sighted.
Also Friday, a Ukrainian military spokesman said a shell landed in the rebel-controlled Luhansk area, killing a 5-year-old girl. It was unclear who had fired the shell.
There has been a surge in fighting between government and separatist forces since the cease-fire agreement was signed, with each side accusing the other of violating the agreement and shelling civilian areas.
In an interview with the German newspaper Rheinische Post, Ukraine's foreign minister, Pavlo Klimkin, said his government was not planning a military operation to regain control over those parts of eastern Ukraine controlled by the separatists.