The move could give Russian President Vladimir Putin every reason to delay discussions about pausing the fighting in favour of seeking more land, the Ukrainian officials said.
They maintain Russia has no intention of engaging in meaningful dialogue to end the war.
With the spring fighting season drawing near, the Kremlin is eyeing a multi-pronged push across the 1000-kilometre frontline, according to analysts and military commanders.
Citing intelligence reports, Ukrainian President Volodymyr Zelenskiy said Russia is getting ready for new offensives in the northeast Sumy, Kharkiv and Zaporizizhia regions.
"They're dragging out the talks and trying to get the US stuck in endless and pointless discussions about fake conditions just to buy time and then try to grab more land," Zelenskiy said Thursday in a visit to Paris.
"Putin wants to negotiate over territory from a stronger position."
Two G7 diplomatic officials in Kyiv agreed with that assessment.
They spoke on the condition of anonymity because they were not authorised to brief the press.
Russia has effectively rejected a US proposal for an immediate and full 30-day halt in the fighting, and the feasibility of a partial ceasefire on the Black Sea was thrown into doubt after Kremlin negotiators imposed far-reaching conditions.
Ukraine's emergency service said four people died and 21 were injured on Friday evening after Russian drones struck Dnipro in the country's east.
At least seven more people were injured when a Russian ballistic missile struck Kryvyi Rih, Zelenskyy's hometown, according to local Governor Serhii Lysak.
Battlefield success is clearly in Putin's mind.
"On the entire front line, the strategic initiative is completely in the hands of the Russian armed forces," Putin said on Thursday at a forum in the Arctic port of Murmansk.
"Our troops, our guys are moving forward and liberating one territory after another, one settlement after another, every day."
Ukrainian military commanders said Russia recently stepped up attacks to improve its tactical positions ahead of the expected broader offensive.
"They need time until May, that's all," said Ukrainian military analyst Pavlo Narozhnyi.
In the north, Russian and North Korean soldiers have nearly deprived Kyiv of an essential bargaining chip by retaking most of Russia's Kursk region, where Ukrainian soldiers staged a daring incursion last year.
Battles have also escalated along the eastern front in Donetsk and Zaporizhzhia.
A concern among some commanders is whether Russia might divert battle-hardened forces from Kursk to other parts of the east.
"It will be hard. The forces from Kursk will come on a high from their wins there," said a Ukrainian battalion commander in the Donetsk region, who spoke on condition of anonymity.
"They are preparing offensive actions on the front that should last from six to nine months, almost all of 2025," said Ukrainian military analyst Oleksii Hetman.
Russia entered negotiations with a clear advantage in the war.
Now, after recapturing 80 per cent of its territory in the Kursk region ahead of talks, its forces have intensified their fighting across other parts of the front line.
"The number of clashes on the front line is not decreasing," Hetman said.
"If they wanted to stop the war, their actions certainly don't show it."
Russia ramped up reconnaissance missions to find and destroy firing positions, drone systems and other capabilities that could impede a future onslaught, two Ukrainian commanders said.
"These can be all signs that an attack is being prepared in the near future," Hetman said.
