US officials were upbeat Tuesday about the drive to end the war in Ukraine but acknowledged that sticking points remain over a US plan to halt the nearly four-year conflict.
The United States is pushing Ukraine to accept proposals which Kyiv says concede too much to Moscow.
Talks between US Army Secretary Dan Driscoll and Russia delegates on the US plan were progressing, his spokesman said.
"Late Monday and throughout Tuesday, Secretary Driscoll and team have been in discussions with the Russian delegation to achieve a lasting peace in Ukraine," said Lieutenant Colonel Jeff Tolbert, Driscoll's spokesman. "The talks are going well and we remain optimistic."
The White House said that remaining issues in talks to end Russia's war against Ukraine would require more negotiation.
"The United States has made tremendous progress towards a peace deal," press secretary Karoline Leavitt posted on X.
"There are a few delicate but not insurmountable details that must be sorted out and will require further talks between Ukraine, Russia, and the United States."
Driscoll was meeting with a Russian delegation in Abu Dhabi on Tuesday, US and British media reported, days after talks with Ukraine in Geneva aimed at ending the conflict.
Driscoll met the Russian delegation on Monday with talks due to continue on Tuesday, ABC News and the Financial Times reported, citing a US official.
Several US media outlets reported Tuesday that a US official has said Ukraine accepted a peace deal.
The latest talks were previously undisclosed, and follow meetings held in Switzerland between US and Ukrainian officials aimed at resolving the war with Russia.
The Financial Times said the head of Ukrainian military intelligence, Kyrylo Budanov, would be present at the talks, without detailing the Russian officials.
"Driscoll has been involved with this peace process pretty hot and heavy in the past few days," a US official told the Financial Times, without being named.
"Obviously, Ukraine knows what's going on, they knew where he was coming" after Geneva, he added, according to the paper.
Kremlin spokesman Dmitry Peskov neither confirmed nor denied the meetings.
The US plan, originally made up of 28 points, would see Ukraine effectively cede its eastern Donetsk and Lugansk regions to Russia and slash the size of its military -- demands that Kyiv has described as unacceptable.
