Ukrainian President Petro Poroshenko and NATO Secretary-General Anders Fogh Rasmussen have expressed cautious optimism about an anticipated ceasefire on Friday between Ukraine and pro-Russian rebels fighting in the country's east.

I have "careful optimism," said Poroshenko, who said Ukraine pays "the highest price every single day" of the conflict with the loss of soldiers and innocent civilians.

Rasmussen said he welcomes the ceasefire, if it is a genuine effort on Russia's part for peace in the region. But he cautioned that similar earlier statements have simply been "a smokescreen" for Russia to further destabilize Ukraine.

Rasmussen pledged NATO's unwavering support to embattled Ukraine at a news conference at the two-day NATO leaders summit in Wales.

"We stand united with Ukraine," he said.  "We strongly condemn Russia's repeated violations of international law."

NATO's support was applauded by Poroshenko, who said he has never felt such enormous support before.

Ceasefire conditional on talks

Ukraine and the pro-Russian separatists appeared increasingly close to signing a deal to end four months of fighting, even as Ukraine's leader met Thursday with President Barack Obama and other NATO leaders in Wales.

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A pro-Russian separatist guards his position at a checkpoint outside the village of Kreminets near the city of Donetsk, eastern Ukraine. (Maxim Shemetov/Reuters)

Earlier, Poroshenko said he would order a ceasefire on Friday, paving the way for implementation of a "stage-by-stage peace plan" for his country.

Speaking on the sidelines of the NATO summit, Poroshenko said that the ceasefire was conditional on a planned meeting going ahead in Minsk on Friday of envoys from Ukraine, Russia and Europe's OSCE security watchdog. 

"At [7 a.m. ET on Friday], provided the [Minsk] meeting takes place, I will call on the General Staff to set up a bilateral ceasefire and we hope that the implementation of the peace plan will begin tomorrow," Poroshenko said.

The rebels also said they were ready to declare a truce Friday if an agreement with Ukraine is reached on a political settlement for the mostly Russian-speaking region.

Rebel leaders in eastern Ukraine made proposals on Thursday that echoed a plan outlined by Russian President Vladimir Putin, according to details cited by Russian news agency Interfax.

Leaders of the self-declared Donetsk and Luhansk People's Republics proposed the creation of a "security zone" split into five sections, each of which would be monitored by 40 observers from OSCE.

Rebels also said they would allow a humanitarian corridor for refugees and aid as part of the proposed ceasefire "in order to stabilise the situation and stop the bloodshed."

Facing major challenges with conflicts in Ukraine, Syria and Iraq and a winding down of operations in Afghanistan, NATO leaders gathered for a two-day summit at a golf resort in southern Wales. Before the official proceedings began, Poroshenko attended a meeting with Obama and the leaders of NATO's four major European powers: British Prime Minister David Cameron, French President François Hollande, German Chancellor Angela Merkel and Italian Prime Minister Matteo Renzi.

Moscow denies it has troops in Ukraine but NATO says more than 1,000 Russian soldiers are operating in the country. Rasmussen also said NATO allies would consider seriously any request from Iraq for assistance in dealing with the growing insurgency by Sunni militants.

Potential rift within NATO

Poroshenko is expected to meet with the heads of state and government from all 28 NATO member states later on Thursday.

The Ukrainian leader is looking for arms, training and intelligence support for his armed forces as well as political support against Russian President Vladimir Putin. 

However, his talk of reviving Ukraine's bid to join the U.S.-led military alliance could reopen a rift within NATO.

Under Article 5 of the NATO charter, an attack on one member state is viewed an an attack on the whole alliance. Were Ukraine to join NATO, alliance members would be obliged to defend it with arms. As it is not a member, they have made clear they will not fight to protect it, but are taking mainly economic measures — U.S. and EU sanctions — against Russia. 

Obama reiterated his support for that principle Wednesday during a visit to Estonia, one of the newer NATO members set on edge by Russia's provocations. He said the door to membership would remain open to states that meet NATO standards and "can make meaningful contributions to allied security," but France and Germany remain opposed to admitting Kyiv.

A French official said NATO should contribute to easing tensions, not exacerbating them.

Russia warns against Ukraine joining NATO

Russian Foreign Minister Sergei Lavrov underlined Moscow's opposition to Ukraine joining NATO, warning that attempts to end the country's non-aligned status could "derail all efforts aimed at initiating a dialogue with the aim of ensuring national security."

As more than a decade of NATO-led combat operations in Afghanistan draws to a close at year's end, the 28-nation, U.S.-led military alliance is refocusing in part on its core task of defending its territory.

NATO leaders will set up a "spearhead" rapid reaction force, potentially including several thousand troops, that could be sent to a hotspot in as little as two days, officials say.

Eastern European NATO members, including Poland, have appealed to NATO to permanently station thousands of troops on their territory to deter any possible Russian attack.

But NATO members have spurned that idea, partly because of the expense and partly because they do not want to break a 1997 agreement with Russia under which NATO committed not to permanently station significant combat forces in the east.

Instead, leaders will agree to pre-position equipment and supplies, such as fuel and ammunition, in eastern European countries with bases ready to receive the NATO rapid reaction force if needed.

NATO has said it has no plans to intervene militarily in Ukraine. It has focused on beefing up the defences of former Soviet bloc eastern European countries that joined the alliance in the last 15 years. The Baltic states Latvia, Lithuania and Estonia, the only parts of the former Soviet Union itself to be admitted to NATO, fear Moscow could meddle in their affairs with the same rationale it applied in Ukraine — protecting Russians.

With files from the Associated Press, CBC News