As Moscow considered the plan, President Vladimir Putin, dressed in military fatigues, made a surprise visit to Russia's Kursk region for the first time since Ukrainian troops captured part of it last year.
With Putin's presence highlighting recent Russian advances in Kursk, Valery Gerasimov, head of Russia's General Staff, told the Kremlin leader his troops had repelled Ukrainian forces from 86 per cent of the ground they once held in Kursk. Ukraine had hoped to use that territory as a bargaining chip in any peace talks with Moscow.
But Ukraine's top army commander Oleksandr Syrskyi said on Facebook that fighting continued on the outskirts of Sudzha town in Kursk and Kyiv's troops will continue operating there "as long as appropriate and necessary."
The US on Tuesday agreed to resume weapons supplies and intelligence sharing after Kyiv said at talks in Saudi Arabia that it was ready to support a ceasefire proposal.
The Kremlin said it was carefully studying the results of that meeting and awaited details from Rubio and White House National Security Adviser Mike Waltz. Later on Wednesday, the White House said Waltz had spoken with his Russian counterpart.
Speaking to reporters when his plane refuelled in Ireland, Rubio said: "Here's what we'd like the world to look like in a few days: Neither side is shooting at each other, not rockets, not missiles, not bullets, nothing ... and the talking starts."
Two people familiar with the matter said Russia has presented Washington with a list of demands for a deal to end the Ukraine war and reset relations with the United States.
The specific demands were not clear, nor whether Russia, which holds just under a fifth of Ukraine, was willing to enter peace talks with Kyiv prior to their acceptance.
The people said the demands were similar to previous Kremlin terms including no NATO membership for Kyiv, recognition of Russia's claim to Crimea and four Ukrainian provinces and an agreement that foreign troops not be deployed in Ukraine.
In Washington, President Donald Trump told reporters at the White House that he had received "positive messages" about the potential for a truce in the three-year-old conflict, without giving details.
After Russian forces made gains in Ukraine in 2024, Trump reversed US policy on the war, launching bilateral talks with Moscow and suspending military assistance to Ukraine, demanding that it take steps to end the conflict.
Rubio said Europe would have to be involved in any security guarantee for Ukraine, and that the sanctions Europe has imposed would also be on the table.
After a meeting of five European defence ministers, British defence minister John Healey on Wednesday told reporters that work was accelerating on a "coalition of the willing from Europe and beyond" to support Ukraine. French Defence Minister Sebastien Lecornu said about 15 countries had expressed interest.
Asked whether Russia could accept the ceasefire unconditionally, Rubio said: "That's what we want to know - whether they're prepared to do it unconditionally."
In Kyiv, Ukrainian President Volodymyr Zelenskiy hailed this week's meeting in Saudi Arabia between US and Ukrainian officials as constructive, and said a potential 30-day ceasefire with Russia could be used to draft a broader peace deal.
Russia's invasion of Ukraine in early 2022 has left hundreds of thousands of dead and injured, displaced millions of people, reduced towns to rubble and triggered the biggest confrontation between Moscow and the West in six decades.
Putin called for Kyiv's troops in Kursk to be completely defeated. He also made it clear he was considering the creation of a buffer zone in Ukraine's Sumy region, across the border from Kursk.
Deep State, an authoritative Ukrainian site that charts the frontlines of the war, updated its battlefield map to show Ukrainian forces were no longer in control of Sudzha. However, it said fighting was continuing on the outskirts.
