Fighting has subsided in eastern Ukraine since the deal was signed in Minsk, Belarus, in February last year.
It provided for a cease-fire as well as a political transition in Ukraine's industrial heartland, where fighting has killed over 9,200 people.
Denis Pushilin, who represents the rebels in Minsk, was quoted by the rebel mouthpiece Donetsk News Agency on Friday as saying that the way the truce is being implemented right now, it could take 10 to 15 years to comply with all of its statures.
The step-by-step Minsk plan was linked to the withdrawal of heavy weaponry and was not supposed to drag on for years.
The cease-fire is constantly violated by both sides and crucial elements of the political settlement, such as holding local elections in rebel-occupied territories and ensuring the rebels hand over the control of parts of the border with Russia to Ukraine, have not been implemented.
Meanwhile, both sides on Friday traded accusations of cease-fire violations Thursday night.
Andriy Lysenko, presidential spokesman for Ukrainian forces in the east, said one Ukrainian has been killed by an unspecified explosive device and three troops have been injured in fighting in the past 24 hours.