US Secretary of State John Kerry remains optimistic about the outcome of peace negotiations in eastern Ukraine despite accusing rebel forces of a "piecemeal" approach to the ceasefire agreement.

The rebel soldiers are pro-Russian separatists that declared secession from the Ukraine after Russia annexed the Crimea in March last year.

Reuters reported last month that negotiations between the two forces fell through as each side accused each other of sabotaging an earlier ceasefire agreement signed in September last year. The Organisation for Security and Cooperation in Europe (OSCE) said the rebels were unprepared to implement the September agreement, while the rebels accused the Ukrainian government of deliberately attacking civilian areas in the front lines.

A new agreement was announced on February 15 by the leaders of Russia, Ukraine, Germany and France, under which both the Ukrainian government forces and the rebel soldiers were to withdraw from the front lines and take their heavy weapons with them. The withdrawal was scheduled to be completed by the end of February.

According to the BBC however, Mr Kerry told the UN Human Rights Council on Monday that the rebel forces were removing their heavy weaponry only from select areas on the front line.

Despite the setback, he remains optimistic about the truce, stating that it can be completed in a matter of hours, and not more than a few days.

"I'm very hopeful that it will in fact be the start of a change which would be an improvement for everybody," Mr Kerry said at a news conference in Geneva.

Meanwhile, both government and rebel forces are reporting troop and weapon withdrawals as dictated by the ceasefire agreement, the BBC reports. OSCE monitors on the front lines have verified this, but they also stated that they cannot yet confirm a full withdrawal from both sides as it is still "too early."