U.S. President Barack Obama said Monday no decision had been made on whether to send weapons to Ukraine to help Kiev battle pro-Russian separatists, as he warned the West would not allow Russia to redraw Europe's borders by force.

Obama, who has faced increasing calls from domestic critics to supply the outmatched Ukrainian army with more weapons to shore up its faltering defenses, said he was still mulling his options.

Germany's economy minister on Monday rejected calls by Greece's new prime minister for Berlin to pay reparations for World War II damages by the Nazis, insisting the issue was concluded 25 years ago.

"The likelihood is zero," Sigmar Gabriel, who is also Germany's vice-chancellor, said at a gathering of his Social Democrats in Brandenburg state near Berlin.

Spanish police said Monday they arrested a British man accused of killing a German for filming his young daughter in a restaurant in a posh seaside resort.

The Briton, aged 40, attacked the 43-year-old German after seeing him filming the minor with a tablet device in the restaurant near the yacht-packed port in Sotogrande on Spain's Costa del Sol on Saturday night.

Russia said Monday that President Vladimir Putin would not tolerate any ultimatums over Ukraine after a report said Germany had given him until Wednesday to agree a peace plan or face new sanctions.

"We've already said everything about the tone of the negotiations," Putin's spokesman Dmitry Peskov said on Russian radio.

German Chancellor Angela Merkel was Monday to brief U.S. President Barack Obama on the latest peace plan for Ukraine ahead of a four-way summit aimed at ending 10 months of bloodshed.

Foreign ministry officials from Ukraine, Russia, Germany and France were due to hold a preparatory meeting in Berlin after leaders agreed to push for the key meeting on a new peace deal Wednesday in Minsk, the capital of Belarus.

The United States is weighing "additional" assistance to Ukraine as it battles Russian-backed separatists, Secretary of State John Kerry said Saturday, while stopping short of saying Washington would send arms.

Kerry's comments came as Western leaders challenged Russian President Vladimir Putin to prove he wants peace in Ukraine, warning both sides a new Franco-German peace drive may be a "last chance" to stop all-out war.

German Chancellor Angela Merkel on Saturday pushed a new peace bid to end the Ukraine conflict, warning that sending weapons to government forces fighting pro-Russian rebels would not stop the bloodshed.

Fresh from overnight talks in Moscow with French President Francois Hollande to thrash out a new peace plan, Merkel said success was far from assured but it was essential to try.

Prime Minister Tammam Salam noted on Friday that the presence of refugees in a country of such fragile economic and political scenes as Lebanon is a “ticking time bomb”.

He said: “The large number of Syrian refugees in Lebanon has led to an increase in crime due to unemployment and poverty.”

Prime Minister Tammam Salam arrived Thursday in Germany at the head of a ministerial delegation to take part in the three-day Munich Security Conference (MSC).

Salam is expected to address around midnight Friday more than 40 heads of government and state, along with 60-odd foreign and defense ministers including U.S. Secretary of State John Kerry and Russia's top diplomat Sergei Lavrov.

German prosecutors charged an 18-year-old man on Tuesday over the death of a young German-Turkish woman who has become a symbol of civic courage for giving her life trying to protect two teenage girls.

The suspect faces a charge of assault leading to death in the case in which student teacher Tugce Albayrak, 23, received a blow to the head in a car park outside a McDonald's restaurant on November 15.