President Obama spoke from the NATO Summit in Wales following a cease-fire agreement between Ukraine and pro-Russia separatists.

Here's more background on the agreement:

MINSK, Belarus (AP) -- President Petro Poroshenko said he ordered government forces to stop hostilities at 1500 GMT (11 a.m. EDT) following a protocol signed by representatives of Ukraine, Russia, the rebels and the Organization for Security and Cooperation in Europe.

"Human life is of the highest value. And we need to do everything that is possible and impossible to stop bloodshed and end people's suffering," Poroshenko said in a statement.

Heidi Tagliavini of the OSCE told reporters the deal in the Belarusian capital focused on 12 separate points but she did not immediately spell them out before heading back into the talks. Poroshenko said a prisoner exchange would begin Saturday and international monitors would keep watch over the cease-fire.

With the cease-fire deal, Putin may hope to avert a new round of sanctions, which the European Union leaders ordered Friday to be prepared.

Since mid-April, Moscow-backed separatists have been fighting government troops in eastern Ukraine in a conflict the U.N. estimates has killed nearly 2,600 people.

"The cease-fire will allow us to save not only civilians lives, but also the lives of the people who took up arms in order to defend their land and ideals," said Alexander Zakharchenko, the rebel leader from the Donetsk region.

But Igor Plotnitsky, leader of the separatist Luhansk region, told reporters "this doesn't mean that our course for secession is over" -- a statement that reflected the deep divisions which threaten to derail peace efforts.

Details of the peace plan are yet to be released. Putin has suggested earlier this week that rebels halt their offensive and Ukrainian government forces stop using combat aircraft and pull back so they can't shell residential areas with artillery and rockets. Poroshenko, in his turn, has emphasized that Russia must withdraw its troops from Ukraine.

Moscow has denied reports by Ukraine, NATO and Western nations that it was backing the mutiny with weapons, supplies, and even with thousands of regular troops. But a NATO military officer told The Associated Press on Thursday that the ranks of Russian soldiers directly involved in the conflict have grown even past NATO's earlier estimate of at least 1,000.

At a summit in Wales, NATO leaders approved plans Friday to create a rapid response force with a headquarters in Eastern Europe that could quickly mobilize if an alliance country in the region were to come under attack. Ukraine is not a NATO member, but the entire alliance has been alarmed by Russia's actions in Ukraine, and Russia is under both U.S. and EU sanctions for its backing of the rebels.

In his statement, Poroshenko said he ordered the cease-fire following Putin's call on the insurgents to halt fighting. He said he expects the OSCE to efficiently monitor the cease-fire.

"I count on this agreement, including the ceasing of fire and the freeing of hostages, to be precisely observed," Poroshenko said. 

Obama said he is "hopeful" that hostilities will end, but is "skeptical" that pro-Russian separatists will abide by it. He touted the effectiveness of the sanctions that have already been enacted against Russia.

"Today the United States and Europe are finalizing measures to deepen and broaden our sanctions across Russia's financial, energy, and defense sectors. At the same time we strongly support President Poroshenko's efforts to pursue a peaceful resolution to the conflict in his country," said Obama.

He said NATO agreed on creating a "highly ready rapid response force" that can be deployed on short notice and increasing the alliance's presence in eastern and central Europe

Watch his full opening remarks above.