US President Donald Trump and Russian counterpart Vladimir Putin are expected to speak this week, officials said on Sunday, as Washington and Kyiv's European allies press Moscow to accept a ceasefire in the three-year war.
The United States this week proposed a halt in fighting in the war after talks in Saudi Arabia, with Kyiv accepting the proposal.
Putin however has given no clear answer, instead listing a string of conditions and raising "serious questions" over the proposition.
Trump's envoy for the conflict, Steve Witkoff, who met for several hours with Putin days ago, told CNN in a televised interview that he thinks "the two presidents are going to have a really good and positive discussion this week."
Earlier the Moscow said that US Secretary of State Marco Rubio called his Russian counterpart Sergei Lavrov and that the pair had discussed "concrete aspects of the implementation of understandings" at a US-Russia summit in Saudi Arabia last month.
Ukraine's Volodymyr Zelensky on Saturday accused the Kremlin of not wanting to end the war and warned that Moscow wanted to first "improve their situation on the battlefield" before agreeing to any ceasefire.
The February Riyadh gathering was the first high-level meeting between the United States and Russia since Moscow launched its attack in February 2022.
"Sergei Lavrov and Marco Rubio agreed to remain in contact," the Russian foreign ministry said, with no mention of the US-suggested ceasefire.
State Department spokeswoman Tammy Bruce said Saturday that the pair had "discussed the next steps" on Ukraine.
She also said Rubio and Lavrov "agreed to continue working towards restoring communication between the United States and Russia".
The Lavrov-Rubio call came hours after the UK hosted a virtual summit on Ukraine, with Prime Minister Keir Starmer accusing Putin of "dragging his feet" on the ceasefire.
"The 'yes, but' from Russia is not good enough," Starmer said, calling for a stop to the "barbaric attacks on Ukraine once and for all".
Kyiv the next day said Russia launched 90 Iranian-made Shahed drones onto nine Ukrainian regions.
Zelensky says Putin 'lying'
In his reaction to the ceasefire earlier this week, Putin said the initiative would benefit primarily Ukraine and not Russian forces, who he said are "advancing" in many areas.
He raised "serious questions" over the initiative.
The proposal came as Russia - which occupies swathes of southern and eastern Ukraine - has had momentum in some areas of the front.
It has ousted Ukrainian forces from parts of its Kursk region, where Kyiv hopes to hold onto Russian territory as a potential bargaining chip in any future negotiations.
Putin said he wanted to discuss Moscow's concerns with Trump in a phone call.
Zelensky said Saturday that by not agreeing to the ceasefire, Putin was also going against Trump - who has made overtures towards Russia - and accused Moscow of trying to find ways not to end the war.
He accused Putin of "lying about how a ceasefire is supposedly too complicated".
Ukraine said Sunday that one person was killed by a Russian drone strike on the city of Izyum - in the Kharkiv region, which fell to Russia at the start of its Ukraine attack before being retaken by Kyiv's forces.
