Moscow has not officially contacted Kyiv about peace negotiations, but Russia would in any case need to completely withdraw its forces for talks to take place, a top Ukrainian official said on Saturday.

"We have not any official application from the Russian side about... negotiations," Andriy Yermak, the Ukrainian presidential chief of staff, said in English remarks made via video link at the Halifax International Security Forum.

Any talks not based on Ukrainian sovereignty and territorial integrity within the limits of its internationally recognised borders are "not acceptable," he said.

"The first steps it's necessary to do from the Russian side is to withdraw all Russian troops from Ukrainian territory," Yermak added.

His remarks came a day after Ukrainian President Volodymyr Zelenskyy dismissed the idea of a "short truce" with Russia, saying it would only make things worse.

"Russia is now looking for a short truce, a respite to regain strength. Someone may call this the war's end, but such a respite will only worsen the situation," the Ukrainian leader said in remarks broadcast at the same security forum.

"A truly real, long-lasting and honest peace can only be the result of the complete demolition of Russian aggression," Zelenskyy said.

The White House said on Friday that only Zelenskyy can decide when to open peace talks with Russia, rejecting the notion that it was pressing Kyiv to negotiate an end to the nearly nine-month war sparked by Moscow's February assault.

General Mark Milley, the top US military officer, has however suggested in recent weeks that Kyiv could take advantage of battlefield victories over Moscow's forces and open talks toward ending the conflict.

Milley said on Wednesday that while Ukraine has achieved key successes, Moscow still controls some 20 percent of the country, and that it is unlikely Kyiv's troops will force the Russians to quit the country soon. (AFP)