Putin and Poroshenko are due to meet in the Belarussian capital Minsk on Tuesday at a meeting that will also include senior members of the European Union and the Russian-led Customs Union.
"My visit to Kiev was preparation for such a meeting (between Putin and Poroshenko) which certainly won't result in the breakthrough," said Merkel in an interview with ARD television.
"But you have to talk to each other if you want to find solutions," said Merkel, adding the situation was very fragile.
Merkel, who has tried to play a role in easing the crisis, said she would do everything possible to help the two sides overcome differences on questions from decentralisation to trading ties and gas deliveries.
"What we say, and especially I as someone who experienced how Germany could be united peacefully with the agreement of its neighbours, say that the Ukrainian people must have the opportunity to choose their path," she said.
Merkel, brought up in Communist East Germany, said she did not want to do anything that would hurt Russia, indeed she wanted to have good trading and diplomatic relations with Moscow.