Prime Minister Arseniy Yatsenyuk, in an interview at his office in Kiev, said Russia was uninterested in de-escalating Ukraine's conflict with separatist forces, despite its commitment to maintain a peace deal made in February.
Ukraine and the West accuse Russia of being directly involved in the separatist conflict in eastern Ukraine which has left over 6,000 dead in the last year.
Moscow denies that charge.
The warring sides are poised in a delicate truce that is largely holding, despite sporadic skirmishes along the 450-kilometer (280-mile) front line.
The cease-fire agreement reached in February requires both Ukraine government and rebel forces to pull back their heavy weapons.
It also envisions Ukraine granting its rebellious eastern territories some measure of self-rule.
Yatsenyuk told the AP in an English-language interview that the agreement was a bad but necessary settlement that could halt new rebel advances.
"This is a political solution. A diplomatically political solution, which has to be underpinned by the military capabilities of the Ukrainian army," he said.
"The idea is just to deter the Russian terrorists, not to allow them to move further."
The prime minister said the West must stay united in helping Ukraine repel Russian aggression and that achieving this would be the "joint success of the entire free world."
The European Union and the United States have slapped sanctions on Russia for its actions in Ukraine, a move that has hurt the Russian economy.
Russian President Vladimir Putin's "main focus today is on the EU," Yatsenyuk said.
"To split the unity among the EU member states, to lift sanctions. And to split the unity among the United States of America and the European Union."
The Ukrainian government's detractors have sought to paint it as crippled by corruption and divisions within its national leadership and weighed down by a plummeting economy.
Ukraine has begun addressing shortcomings in all those areas, Yatsenyuk said.
On Wednesday, police officers barged into a televised government meeting to detain two top officials on suspicion of extorting bribes.
Yatsenyuk indicated that would set the pace for his government's looming fight against graft.
"It is disgusting when the country is in the state of war and high-profile officials are just stealing the money from the pockets of ordinary Ukrainians," he said.
"Everyone who violates the law, who commits any kind of corruption, will be brought to justice."
The International Monetary Fund earlier in March agreed to extend $17.5 billion in loans to Ukraine as part of a program designed to pull the country back from the verge of economic collapse.
Yatsenyuk said that kind of support would head off the default that many economic experts have predicted for Ukraine.
"This is the way how to stabilize the economic situation, how to stabilize the (foreign exchange rate), and how to repay out debts to our creditors," he said.
Just how successful Ukraine will be in handling repayment of its onerous debts, however, will depend on accommodations by its creditors, which include Russia.
Yatsenyuk played down persistent rumors of fissures within the national leadership, particularly between himself and President Petro Poroshenko.
Anxiety at infighting among Ukraine's elite was compounded this week after Poroshenko was compelled to dismiss the truculent billionaire governor of an eastern region.
"We are fully and entirely united," Yatsenyuk insisted.
"We are floating in the same boat. And we are not eager to sink. We want to float."
The austerity required by international creditors is pressing down on already-low standards of living in Ukraine.
Yatsenyuk rattled off a series of harsh changes implemented by his government, which have included increases in taxes, a reduction in social entitlement programs and a freeze in state salaries.
"We've closed a number of tax loopholes. We've increased communal tariffs by six times. We've fired 10 percent of public servants," he said, sighing heavily.
Yatsenyuk said the ultimate goal of enduring the financial pain was to create a country with a clear sense of national purpose.
"A few years ago we had the territory. Today, we have the country. An independent country that is fighting for freedoms and liberties," he said.