NATO's top military commander on Saturday said Russian forces were still operating in Ukraine and that a ceasefire was not working, but he expressed hope a new peace plan could bring progress.

"As to Russian forces on the ground, yes, they are still inside Ukraine," US General Philip Breedlove told reporters in Lithuania, without providing precise numbers.

He said a two-week-old ceasefire was "still there in name, but what is happening on the ground is quite a different story. We hope that this will change."

"The fluidity of movement of Russian forces and Russian-backed forces back and forth across that border makes it almost impossible to understand the numbers," he said in Lithuania's capital Vilnius, where NATO military chiefs met this weekend to focus on the alliance's eastern flank and ties with Russia.

Breedlove said the number of Russian troops inside Ukraine had "come down significantly" from what he termed the "height" of Russian movement into Ukraine "over a week ago".

But he insisted "they haven't returned home and are still available to bring their military force to bear on Ukraine should it be desired."

"And then of course we have seen Russian forces reposition inside the country to bring great pressure on Mariupol in the south.

"So the short answer is yes, there are still Russians inside of Ukraine enabling the Russian-backed forces there."

But he was hopeful about a nine-point peace plan agreed in marathon overnight talks in the Belarussian capital Minsk, which calls on Ukrainian forces and pro-Russian militias to pull back their troops from a demilitarised zone in eastern Ukraine.

"We heard today of some possible new agreements... and it is our sincere hope and desire that... the two combatants can come to agreement to again get to a ceasefire situation," he said.

Under the freshly agreed Minsk pact, forces from both sides are required to retreat 15 kilometres (9.3 miles) from current frontlines within 24 hours of the signing of the accord and allow monitors from the OSCE pan-European security organisation into the area to make sure the truce holds.

Territory under rebel control would be left open to their administration under a temporary self-rule plan adopted by lawmakers in Kiev on Tuesday.

The pact -- also signed by Moscow's ambassador to Kiev and the self-proclaimed "prime ministers" of the rebel-run regions of Donetsk and Lugansk -- aims to shore up a ceasefire deal signed on September 5.

- Afghan deal -

Breedlove also said NATO was eyeing the rapid conclusion of security agreements with Afghanistan for its post-2014 mission in the country once a unity government is formed there.

"We are hoping for very fast signatures," he said, adding that the rival candidates both endorsed crucial security pacts that will allow NATO troops to stay in Afghanistan after the end of this year.

The result of Afghanistan's disputed election is due to be declared on Sunday.

The stalemate between presidential candidates Ashraf Ghani and Abdullah Abdullah since the June 14 vote has plunged Afghanistan into a political crisis as US-led NATO troops end their 13-year war against the Taliban.

NATO's combat mission will end in December, with a follow-on force of about 12,000 troops likely to stay into 2015 on training and support duties.

The talks in Lithuania focusing on defending NATO's eastern flank and relations with Russia come just two weeks after the alliance announced a new rapid reaction force at a key summit in Wales.

Lithuania said the new measures will also include regional "command and control" centres in the Baltic states and Poland.

These countries, formerly behind the Iron Curtain, are concerned about Russia's territorial ambitions in view of the Crimea annexation and the conflict in eastern Ukraine.