MOSCOW, Russia (AFP) — Russian President Vladimir Putin on Thursday said that he had "serious questions" about Washington's plan for a 30-day ceasefire in Ukraine but Moscow was ready to discuss it with United States President Donald Trump.

Putin made his first comments on the plan, which Ukraine agreed to on Tuesday at talks with the US, saying he was "for" the proposed ceasefire, but that "there are nuances" and he had "serious questions" about how it would work.

Ukrainian President Volodymyr Zelensky condemned Putin's comments as "very manipulative," suggesting in his nightly address that Putin is "actually preparing a refusal" to the proposal, but "is afraid to say directly to President Trump that he wants to continue this war."

The US has called for Russia to agree a ceasefire without any conditions but Putin raised a number of objections, saying: "I think we need to talk to our American colleagues... Maybe have a telephone call with President Trump and discuss this with him."

Putin said a ceasefire was "the right idea," but would benefit Ukraine at a point when its troops are suffering setbacks while Russia is rapidly capturing territory. He also questioned how a ceasefire would be monitored along a front line measuring thousands of kilometers.

Trump said Putin's statement was "promising" but "not complete."

"A lot of the details of a final agreement have actually been discussed. Now we're going to see if Russia is there and, if not, it will be a very disappointing moment for the world," Trump said.

"I'd love to meet with him or talk to him. But we have to get it over with fast."

After visiting a military headquarters in the Kursk region on Wednesday, the Russian president hailed his troops' progress against Ukraine, saying they were "advancing in practically all areas" of the front line.

He said that "based on how the situation on the ground develops, we will agree on the next steps on ending the conflict and reaching agreements acceptable to all."

As Trump pushes for a speedy end to the more than three-year-long conflict, his envoy Steve Witkoff arrived in Moscow on Thursday to discuss the plan.

A top Kremlin aide, Yuri Ushakov, said Witkoff would meet Putin when the president "gives the signal," Russian news agencies reported.

Russia has been grinding forwards on the battlefield for over a year, and claimed on Thursday to have driven Ukrainian forces from the town of Sudzha in Russia's Kursk region.

Trump has expressed optimism that his team can secure a ceasefire, despite Moscow's battlefield gains.