GENEVA, Nov. 23 (Xinhua) -- After further talks with the Ukrainian delegation, U.S. Secretary of State Marco Rubio on Sunday evening declined to reveal any details of the day's discussions in Geneva between the United States, Ukraine, and European partners on a 28-point peace plan.

At a press briefing at around 6 p.m. local time, both the U.S. and Ukrainian sides confirmed "progress" in their earlier talks about the U.S.-proposed plan to end the Russia-Ukraine conflict. Although they told reporters to wait for updates later in the evening, only Rubio returned to the press two and a half hours later.

He said he was not prepared to provide any details on the specific issues under negotiation.

Rubio reiterated that the day's negotiations had been "productive," adding that he remained "very optimistic" about reaching an agreement within a "very reasonable period of time very soon." However, he also noted that "There's no agreement yet … (some) require higher-level decisions and consultation." He added that the differences include semantics or language, and there are still issues "need more time to work through."

"The items that remain open are not insurmountable," he emphasized. He added that some contents involve equities or the role of the European Union or of the North Atlantic Treaty Organization, requiring further discussion with the European partners.

The Ukrainian delegation did not return for a second briefing.

Following the talks, Ukrainian President Volodymyr Zelensky said on social media that it was essential to ensure that "the steps to end the war are effective, and that everything is doable." Enditem