Ukrainian President Volodymyr Zelensky on Thursday threatened to call off a summit with Russian leader Vladimir Putin if all sides do not agree on plans to pull out troops from the east.
The country's comedian-turned-leader is gearing up to hold talks with Putin in Paris in an effort to revive a peace process to end the five-year separatist conflict in eastern Ukraine.
Those efforts appeared to have recently stalled as the Kiev forces and the separatists have so far both failed to pull back troops from the frontline.
"If there is no pullback (of troops) there is no Normandy summit," Zelensky told reporters, referring to talks with Putin that would be hosted by France President Emmanuel Macron and also involve German Chancellor Angela Merkel.
But later, in a response to a question from AFP, he said he still hoped such talks would take place by the end of the year.
A date could be announced as early as next week, he said.
Speaking at a trendy food court during his first major news conference since taking office in May, Zelensky, 41, said Russia should help draw back Kremlin-backed separatist troops.
"They should act as guarantors -- they are party to the Minsk process," Zelensky said during the more than 12-hour event that took place over burgers and pizza at Kyiv Food Market.
In the runup to the planned summit, Ukrainian, Russian and separatist negotiators agreed on a roadmap that envisages special status for separatist territories if they conduct free and fair elections under the Ukrainian constitution.
But the plan sparked anger in Ukraine, with critics saying the proposal favours Russia.
Over the weekend around 10,000 people, including Zelensky's predecessor Petro Poroshenko ,protested in Kiev against the peace plan in the first major demonstrations against Zelensky's policies.
Ultra-nationalists have been particularly critical of Zelensky's peace plan and some war veterans have threatened to resist his orders in the east.
The president appeared to target them on Thursday, saying that "various people" from both sides including Ukraine's war veterans did not want the pullback of troops to go ahead.
"If there are veterans there (in the east)... if they arrived and are armed then that's not right," he said.
Zelensky rapped his critics for trying to "weaken" him, saying that if the current peace plan does not work out "we will look for another option."
Eight hours in to his marathon appearance, Ukraine's National Records Agency declared the press conference the world's longest ever.
- Kremlin blames Ukraine -
Zelensky has pledged he will not betray Ukraine's interests and reiterated Thursday that Kiev should fully control the country's eastern border with Russia.
In Moscow, Putin's top foreign policy advisor, Yury Ushakov, accused "some forces" in Ukraine of attempting to sabotage the peace process.
"Under a far-fetched pretext the Ukrainian side did not begin a troop pullback," Ushakov told reporters.
The ex-Soviet country of 45 million people has gone through two popular uprisings in two decades and has been mired in a war with separatists since 2014.
The conflict -- the worst East-West crisis since the end of the Cold War -- broke out after Russia annexed Crimea in March 2014 and has claimed some 13,000 lives.