German Chancellor Angela Merkel and French President Francois Hollande have arrived in Moscow to discuss a ceasefire and a lasting peace for war-wracked eastern Ukraine with Russian President Vladimir Putin.
The top-level diplomatic dash on Friday came a day after the two leaders met with the Ukrainian government in Kiev to discuss how to salvage a peace plan agreed upon last year in Minsk, Belarus.
Putin's spokesman Dmitry Peskov said in a statement the talks were taking place "eye to eye" between the three leaders without other members of their delegations.
"Everyone is aware that the first step must be the cease-fire, but that it cannot suffice. We must seek a global solution," Hollande told journalists in Paris before heading to Moscow.
Ukrainian President Petro Poroshenko said talks with Merkel and Hollande late on Thursday raised "hope for a ceasefire" after the duo jetted into Kiev in the biggest push yet to resolve the 10-month conflict.
Ahead of the Moscow talks, US Vice President Joseph Biden arrived at the European Union headquarters in Brussels on Friday, to warn against continuing Russian intrusion into Ukraine.
"Russia cannot be allowed to redraw the map of Europe."
"President Putin continues to call for new peace plans as his troops roll through the Ukrainian countryside, and he absolutely ignores every agreement his country has signed in the past."
The frantic diplomacy to end the worst crisis between Russia and the West since the end of the Cold War came as John Kerry, US secretary of state, also visited Kiev, with Washington considering supplying Ukraine with arms to battle pro-Russian rebels.
Few details have emerged of what exactly the new peace proposal contains and there is much disquiet in Kiev after the collapse of previous peace deals, according to Al Jazeera's Rory Challands, who is reporting from Moscow. He said that deployment of UN peacekeepers could be discussed.
Despite the diplomatic momentum behind a new peace plan, Ukrainian Prime Minister Arseniy Yatsenyuk insisted Moscow should just stick to a widely flouted truce accord agreed in Minsk last September.
"To have a new deal, not to execute the previous one, seems to me a trap," Yatsenyuk told journalists.
After his meetings in Kiev, Kerry said that US President Barack Obama would decide "soon" on whether to arm Ukraine, but stressed his preference for a diplomatic solution.
Russia, accused of arming the separatists, warned that any US move to send weapons to Ukraine would cause "colossal damage" to ties, foreign ministry spokesman Alexander Lukashevich said.
Kerry is to meet Russian Foreign Minister Sergei Lavrov at a security conference in Munich on Saturday, ahead of Obama holding a "very important" meeting with Merkel at the White House on Monday, Kerry said.
In a sign of growing international angst over the conflict, NATO on Thursday agreed to a major boost to the alliance's defences near its Russian borders, including six command centres and a quick-reaction spearhead force of 5,000 troops.
As the high-level diplomacy gained pace, the death toll continued to tick up on the ground, with rebels and government officials saying on Thursday that 21 people were killed in 24 hours of clashes.
Al Jazeera's Charles Stratford, reporting from Donetsk, said shelling continued throughout the night, and into the morning on Friday.
"The people continue to live in fear," he said. "There's very little hope in these talks."
The conflict in Ukraine has claimed more than 5,350 lives since April, including some 220 in just the past three weeks, according to the UN.