The move came one day after Russia sent more than 227 alleged humanitarian aid vehicles into eastern Ukraine, enraging Western powers due to violation of international law.
The trucks have since returned to Russia after dropping off their cargo.
Merkel, during a visit to Kiev said the conflict could not be solved through force alone. She denied that Germany's calls for a cease-fire was a criticism of the Ukraine's military offensive against pro-Russian rebels.
During a joint press conference with Poroshenko, she said Germany wouldn't rule out further sanctions against Russia should tensions in eastern Ukraine not be resolved.
Meanwhile, at least three people died Saturday after heavy shelling in the city of Donetsk. Witnesses said the dead were members of a family attempting to flee to a bomb shelter.