Brussels (AFP) - The EU warned Russia Thursday it was ready to take further measures in addition to the sanctions it has already imposed if a new Ukraine peace pact is breached, the bloc's president Donald Tusk said.

"The debate focused on how to support the implementation of the agreement -- if it does not happen we will not hesitate to take the necessary steps," the European Council chief told a press conference after a European Union summit.

The summit focused on the truce deal signed earlier Thursday in the Belarus capital Minsk after marathon talks between the presidents of Ukraine, Russia, Germany and France aimed at ending a 10-month conflict between Kiev and pro-Russian separatists.

Tusk said the EU would go ahead anyway with new sanctions against 19 Russian and Ukrainian individuals and nine entities next week, despite having agreed on Monday to suspend implementation for a week to boost the chances of success of the Minsk talks.

"Our trust in the goodwill of President Putin is limited, this is why we have to maintain our decision on sanctions," he said.

Brussels first imposed targeted sanctions on individuals after Russia's annexation of Crimea in March 2014 but adopted tougher economic measures after the shooting down of Malaysia Airlines flight MH17 over Ukraine in July.

But Tusk said the leaders had not discussed any further sanctions against Russia.

He said Ukrainian President Petro Poroshenko had given EU leaders a "sobering assessment" of the deal and the "terrible situation in his country as a result of Russian aggression."

Poroshenko earlier warned that it would be hard to make a success of the deal between Kiev and pro-Russian separatists.

"It was very difficult negotiation and we expect not easy implementation process," Poroshenko said in Brussels.