Top officials from the United States and Ukraine reported tentative progress on resolving the Russia-Ukraine conflict following high-level discussions on Sunday, but offered few specifics on Washington’s peace proposal, leaving European allies wary of its perceived softness toward Moscow.

U.S. Secretary of State Marco Rubio described the Geneva talks as “very worthwhile,” calling it the most productive day in “a very long time,” and expressed cautious optimism. “I feel very optimistic that we can get something done,” he said, declining to provide details on the discussions.

Rubio downplayed the significance of a Thursday deadline set by President Donald Trump for Ukraine’s response, emphasizing that the immediate priority remains ending the fighting. He suggested that negotiations could extend into Monday and possibly require the involvement of senior officials.

The U.S. has outlined a 28-point plan aimed at ending the nearly four-year conflict, though the proposal has provoked unease in Kyiv and across European capitals over its perceived concessions to Russia.

Diplomats and analysts say the lack of transparency could complicate the peace effort, as Washington balances urgency for a resolution with the concerns of key NATO partners closely monitoring the conflict.