WEIMAR, Germany (Reuters) - The foreign ministers of Germany, France and Poland agreed on Sunday there should be greater international efforts to end the fighting in eastern Ukraine, German Foreign Minister Frank-Walter Steinmeier told reporters.

He said there had not been sufficient progress in implementing the Minsk ceasefire agreement. Western officials were talking with Russia and Ukraine to encourage them to implement measures already agreed in the Minsk process, including communal elections, he said.

"We have to work for a de-escalation of the situation," he told reporters after a meeting with his counterparts aimed at reinvigorating the Weimar Triangle trilateral group.

Steinmeier said the group also wanted to reassure Europeans about the continued importance and relevance of the European Union after the June 23 vote by Britain to exit the bloc.

"The Weimar Triangle can plan an important role ... It is a format where we can discuss progress or the lack of progress on issues such as the Normandy format aimed at ending the Ukraine conflict," Steinmeier said.

The Normandy group comprises Russia, Ukraine, France and Germany.

Steinmeier said fresh efforts began in recent days to revive talks between Russia and Ukraine and pressure both sides to honor agreements they had already made.

The leaders of Russia, Germany and France have agreed to meet to discuss the situation in Ukraine on Sept. 4-5 in China on the sidelines of the G20 summit, the Kremlin said last week.

A recent surge in fighting in eastern Ukraine, where Kiev is fighting pro-Russian separatists, and fresh tension in Crimea have raised concern that a fragile ceasefire agreed in Minsk in February 2015 could collapse.

Ukrainian President Petro Poroshenko said last week he did not rule out introducing martial law and a new wave of military mobilization if the separatist conflict worsened.

(Reporting by Andrea Shalal; editing by Andrew Roche)