KIEV/WASHINGTON/MOSCOW, Dec. 8 (Xinhua) -- Ukrainian President Volodymyr Zelensky said Sunday that talks with U.S. representatives on a peace plan for Ukraine have been "constructive" but "not easy," as he is scheduled to meet European leaders this week.

"The American representatives know the basic Ukrainian positions," Zelensky said in his nightly video address. "The conversation was constructive, although not easy."

Intensive diplomatic efforts have been underway between the relevant parties over the past few days.

On Saturday, U.S. and Ukrainian delegations concluded three-day talks in Miami, Florida, focusing on territorial issues and U.S. security guarantees for Ukraine, U.S. online media outlet Axios reported.

Sources told Axios that the discussion on territory was "difficult," as Kiev has rejected Russia's key demand to withdraw troops from parts of the Donbass that Ukraine continues to occupy, while the United States was trying to develop new ideas to bridge the gap. Another major topic was U.S. security guarantees for Kiev, on which the parties made "significant progress," the report added.

At the end of the Miami talks, Zelensky held a phone call with Trump's special envoy Steve Witkoff and Trump's son-in-law Jared Kushner. Describing the call as "long and substantive," Zelensky said on X that Ukraine remains committed to working with the United States "in good faith" to "genuinely achieve peace."

Zelensky is expected to meet British, French and German leaders in London on Monday, with further talks planned in Brussels.

Meanwhile, Trump claimed on Sunday that Zelensky "isn't ready" to sign off on a U.S-authored peace proposal aimed at ending the crisis.

"I'm a little bit disappointed that President Zelensky hasn't yet read the proposal, that was as of a few hours ago. His people love it, but he hasn't," Trump told reporters before taking part in the Kennedy Center Honors event.

Russian President Vladimir Putin said on Thursday that outstanding issues remain regarding the Ukraine peace plan after his meeting with U.S. envoys at the Kremlin last week.

Moreover, Russia on Sunday welcomed the Trump administration's new national security strategy.

Kremlin spokesman Dmitry Peskov said on Sunday that the adjustments made to the new U.S. National Security Strategy are "largely consistent with our vision," RIA Novosti reported.

Peskov said the new U.S. national security strategy leaves room for hope that joint efforts might result in a peaceful resolution of the Ukraine conflict. "There are phrases opposing confrontation and those favoring dialogue, building good relations. This is what Putin is talking about. This is gratifying, of course," he said.

The White House on Friday released a new national security strategy that paints European allies as weak and aims to reassert America's dominance in the Western Hemisphere.

"It is a core interest of the United States to negotiate an expeditious cessation of hostilities in Ukraine, in order to stabilize European economies, prevent unintended escalation or expansion of the war, and reestablish strategic stability with Russia, as well as to enable the post-hostilities reconstruction of Ukraine to enable its survival as a viable state," the document read. Enditem