After an intense two days of shuttle diplomacy to develop a new plan for ending the fighting in Ukraine, officials from Russia, France, Germany and Ukraine are trying to refine proposals to be discussed on Sunday by the countries' leaders.

A look at where the conflict stands and key issues that must be resolved:

COMBAT

Fighting between Russia-backed separatists and Ukrainian forces in eastern Ukraine has killed more than 5,300 people since it broke out in April, according to a UN tally. More than 1.5 million people have fled the conflict region -- nearly 700,000 of them to neighbouring countries and the rest displaced within Ukraine. The fighting has wreaked severe damage on infrastructure in what was Ukraine's industrial and mining heartland. A pact in September that called for a cease-fire and a pullback of heavy weapons failed to take hold, though all sides say they regard the agreement as key to settling the crisis. Concerns remain high that the rebels aim to take the port city of Mariupol and establish a land corridor between mainland Russia and Crimea, the Black Sea peninsula annexed by Russia 11 months ago.

SANCTIONS

The fighting and the annexation of Crimea have brought relations between Russia and the West into the most severe state since the Cold War. U.S. and European Union sanctions against Moscow have combined with plunging oil prices to drive the Russian economy into dire straits; the ruble has lost half its value over the past year. The sanctions also concern France and Germany, two of Europe's major economies, both of which did substantial trade with Russia.

ARMING THE COMBATANTS

Russia sharply denies Western claims that it is providing equipment and soldiers to the insurgents across the porous border in eastern Ukraine.

President Barack Obama is now pondering whether to heed a rising call for providing lethal weapons to Ukraine, a move that would further strain Washington-Moscow relations. German Chancellor Angela Merkel has bluntly opposed any such U.S. move, saying Saturday that "I cannot imagine any situation in which improved equipment for the Ukrainian army leads to President Putin being so impressed that he believes he will lose militarily."

AUTONOMY

Political questions such as how much autonomy could be granted the eastern regions appear very distant from resolution. The rebels initially aimed for absorption into Russia or independence, but Moscow did not accept their call to be joined into Russia and it has nominally supported Ukraine's territorial integrity -- minus Crimea. French President Francois Hollande said Saturday that some separation is inevitable: "These people have gone to war. It will be difficult to make them share a common life."