The Foreign Secretary welcomed the halt to military operations by the Kiev administration's forces and called on pro-Russia separatists in eastern Ukraine also to lay down their arms.
Mr Hague urged Moscow to use its diplomatic clout to push for an end to the rebellion and stop the transfer of arms across the border.
The Foreign Secretary said: "I welcome President Poroshenko's announcement of a ceasefire. I urge separatists in eastern Ukraine to take this opportunity to lay down their arms and commit themselves to a peaceful resolution of differences.
"The peace plan set out by President Poroshenko is an important step towards this. It is vital Russia now takes immediate steps to help end the violence in eastern Ukraine, including using its influence to encourage separatists to disarm, and stopping the flow of weapons across the border."