"We continue to be realistic about how difficult this is, but optimistic, particularly given the fact that as we've made progress, I think there is a shared vision here that this is not just about ending the war ... it is about securing Ukraine's future, a future that we hope will be more prosperous than it's ever been," Rubio said in Florida, where the talks were being held on Sunday.
Rubio said the aim was to create a pathway that leaves Ukraine sovereign and independent. The discussions follow roughly two weeks of negotiations that began with a US blueprint for peace. Critics said the plan initially favoured Russia, which started the Ukraine conflict with a 2022 invasion.
Ukrainian President Volodymyr Zelenskiy expressed his gratitude to the US team "and to the President personally for the time that is being invested so intensively in defining the steps to end the war".
Special envoy Steve Witkoff and US President Donald Trump's son-in-law, Jared Kushner, were also present representing the US side. Witkoff is expected to meet Russian counterparts later this week.
The high-level negotiations came days before Trump's special envoy, Steve Witkoff, goes to Moscow to meet with Russian leader Vladimir Putin.
Trump has expressed frustration at not being able to end the war.
He pledged as a presidential candidate to do so in one day and has said he was surprised it has been so hard, given what he calls a strong relationship with Putin, who has largely resisted concessions to stop the fighting.
Trump's team has pressured Ukraine to make significant concessions itself, including giving up territory to Russia. The talks shifted on Sunday with a change in leadership from the Ukrainian side.
A new chief negotiator, national security council secretary Rustem Umerov, led the talks for Kyiv after the resignation on Friday of previous team leader Andriy Yermak, chief of staff to Zelenskiy, amid a corruption scandal at home.
As the meeting began, Umerov thanked the US and its officials for their support.
"US is hearing us, US is supporting us, US is walking besides us," Umerov said in English.
After the meeting, he declared the talks productive.
"We discussed all the important matters that are important for Ukraine, for Ukrainian people and US was super supportive," Umerov said.
Zelenskiy had said he expected the results from previous meetings in Geneva would be "hammered out" on Sunday.
In Geneva, Ukraine presented a counter-offer to proposals laid out by US Secretary of the Army Dan Driscoll to leaders in Kyiv some two weeks ago.
Ukraine's leadership, facing a domestic political crisis fuelled by a probe into major graft in the energy sector, is seeking to push back on Moscow-friendly terms as Russian forces grind forward along the front lines of the war.
Last week, Zelenskiy warned Ukrainians, who are weathering widespread blackouts from Russian air strikes on the energy system, that his country was at its most difficult moment yet but pledged not to make a bad deal.
"As a weatherman would say, there's the inherent difficulty in forecasting because the atmosphere is a chaotic system where small changes can lead to large outcomes," Kyiv's first deputy foreign minister Sergiy Kyslytsya, also part of the delegation, wrote on X.
with AP
