First he annexed Crimea. Then he backed rebels in eastern Ukraine. Now Russian President Vladimir Putin is being praised as a peacemaker for endorsing a cease-fire in Ukraine's grinding conflict -- all while neatly short-circuiting Western discussions of new economic and military costs for his role in fueling the war.

The leaders of Ukraine, Germany and France expressed doubts Thursday about the durability of the peace deal they reached with Putin after marathon negotiations in the Belarusan capital, Minsk. So it was left to the Russian leader to claim victory in the efforts to end a nearly year-old war in which he has always denied taking part.

Ukraine committed to politically tricky efforts to grant new freedoms to eastern territories held by pro-Russian rebels. European Union leaders agreed to sit down with the Kremlin to discuss Russian concerns about the Ukrainian government's efforts to align itself with the West. Putin offered little -- but he eliminated, at least for now, the possibility of stronger E.U. sanctions and U.S. arms for Kiev's military.

No wonder he was smiling Thursday when the leaders emerged after their 15-hour talks, which began Wednesday evening and stretched without interruption until Thursday at noon.

"This was not the best night of my life, but the morning in my opinion was good," Putin said in the marble-clad Palace of Independence in Minsk. "Because despite all the difficulties of the negotiation process, we still managed to agree on the essentials."

The cease-fire deal reached Thursday includes the front-line withdrawal of heavy weapons, but powerful disagreements remain over the conflict. The pact is scheduled to take effect Sunday.

Russia has been accused by the West of sending troops and arms to bolster the pro-Moscow separatists in Ukraine. Putin has denied the allegations, although any credible plan to quell the 10-month-old conflict would require the Kremlin's backing.

Still, leaders at the talks in Minsk acknowledged the towering work ahead of them, suggesting that any deal would be fragile. A previous cease-fire accord reached last year fell apart amid escalating fighting.

"We have agreed on many things," Putin told reporters after the talks. "We should avoid unnecessary bloodshed while withdrawing heavy weaponry."

Despite the caution, the deal also is likely to offer some breathing room in a conflict that has brought relations between Russia and the West to lows not seen since the Cold War.

In Washington, White House press secretary Josh Earnest said Thursday that the pact "represents a potentially significant step" toward ending the fighting. However, he noted concern about ongoing clashes, calling them "inconsistent with the spirit of the accord."

In a statement, Earnest called for "immediate, concrete steps to fulfill the commitments by all parties," adding: "The cease-fire must be implemented and honored. Heavy weapons must be withdrawn from the conflict zone, and Russia must end its support for the separatists and withdraw its soldiers and military equipment from eastern Ukraine."

Earnest said, "The true test of today's accord will be in its full and unambiguous implementation."

The White House had said earlier that it would await the outcome of the cease-fire bid before making a decision on whether to send arms to Ukraine's military -- a move strongly opposed by Moscow.

In a separate statement Thursday, Secretary of State John F. Kerry said the United States "will judge the commitment of Russia and the separatists by their actions, not their words." He said the Obama administration "is prepared to consider rolling back sanctions on Russia" when the Minsk cease-fire accords "are fully implemented," including the withdrawal of all foreign troops and equipment from Ukraine, full restoration of government control of borders and the release of all hostages.

The accord offers some concessions to the pro-Russian rebels battling the Western-allied government: a promise that Ukraine would implement constitutional reforms to give rebel-held territories more autonomy.

It also calls for the withdrawal of heavy weaponry at least 30 miles from the front lines -- key steps that should calm violence that has spiked in recent weeks and shocked Europe as it faced the bloodiest conflict on its soil since the Balkan wars of the 1990s.

At least 5,400 people have been killed, according to U.N. estimates, and more than a million people have been pushed from their homes.

"We now have a glimmer of hope," German Chancellor Angela Merkel said. But she also noted that "there are still major hurdles that lie ahead."

"We have no illusions," added Merkel, indicating Putin had put pressure on the rebels to accept the cease-fire.

Among the questions in the 13-point deal is how to monitor the border between Russia and rebel-held zones, and whether Ukraine's Western-backed president, Petro Poroshenko, has the political muscle to carry out his end of the accord.

Poroshenko is likely to face opposition to offer pardons for those involved in the fighting since many government supporters see the rebels as responsible for sparking the violence. Pushing through a new constitution -- including offering greater self-rule to rebel regions -- also will require broad support from lawmakers in Kiev.

Under the deal, Ukraine also agreed to end an economic blockade of rebel-held territories that has cut off pensions, banking services and the movement of goods and people, a key rebel demand.

On the separatist side, meanwhile, a pledge to disband "all illegal groups" may face stiff resistance.

"We were presented with various unacceptable conditions of withdrawal and surrender," Poroshenko told reporters after the talks. "We did not agree to any ultimatums and stated firmly that the cease-fire that is announced is unconditional."

Rebel envoys in Minsk said after the announcement that they were happy about the outcome of the talks.

"This is a major achievement," said one rebel leader, Igor Plotnitsky. "It will help Ukraine to transform itself, to transform in a civilized manner and to stop killing its own people."

Yet even the protocols of the accord reflect the complications and doubts.

The agreement was signed by lower-level representatives from the Ukrainian and Russian governments, along with the two top rebel leaders and a delegate from the Organization for Security and Cooperation in Europe, which is charged with monitoring the cease-fire.

But the national leaders themselves did not sign any such deal, and instead supported a nonbinding statement of support for peace. That suggested they were not willing to commit fully that the deal would be successful.

Poroshenko said the deal envisioned his nation regaining full control of its border by the end of 2015 and that all foreign fighters would be required to leave Ukrainian territory.

But Ukraine also has already lost a key region, the Crimean Peninsula, which was annexed by Russia last year in a move that helped touch off the conflict. The dispute looms as a separate -- and potentially divisive -- backdrop to any peace steps.

Poroshenko also said that Russia had agreed to release imprisoned Ukrainian helicopter navigator Nadiya Savchenko, who has been in Russian custody since last summer and has become a Ukrainian symbol of resistance to the Kremlin and the rebels.

The fundamentals of the deal appeared to be largely the same as a tattered September cease-fire agreement that was never fully observed and has fallen apart completely. Since then, thousands more people have died, and rebels have captured hundreds of square miles of additional territory.

Those battlefield changes mean that it is tricky for the sides to agree on a dividing line for the conflict.

In eastern Ukraine, neither the Ukrainian military nor pro-Russian separatists reported any reduction in violence on Thursday. Both sides reported deaths and casualties from overnight shelling.

There is a chance the two sides could seek to shore up their holdings before the cease-fire takes effect at midnight Sunday.

The worst fighting has centered around two strategic cities in eastern Ukraine: Debaltseve, a rail hub on the border of the Donetsk and Luhansk regions that has been heavily bombarded and rebel leaders claim to have surrounded, and Mariupol, a city between Russia and Crimea on the Sea of Azov where pro-Kiev forces are trying to push back separatists.

Rebel leaders said they have offered Ukrainian troops a safe exit if they surrender in Debaltseve. But the Ukrainian military denies it is surrounded, accusing rebels of simply trying to strengthen their position on the ground.

"Nobody will retreat," said Col. Andriy Lysenko, spokesman for Ukraine's National Security and Defense Council Information Center. He immediately added that the Ukrainian military would, however, follow orders from Kiev on how to comply with the cease-fire.

Meanwhile, Ukraine reached a preliminary accord to expand an International Monetary Fund-led bailout to $40 billion to avert a default. The conflict has battered the Ukrainian economy and drained resources.

In his statement Thursday, Kerry welcomed an agreement between Ukraine and the IMF that he said "will allow the IMF to provide Ukraine with $17.5 billion in financial assistance in support of economic reforms."

Earlier this week, President Obama called Putin to warn that if he did not stop supporting the rebels and come to terms on a peace deal, "the costs for Russia will rise."