Kyiv, Ukraine - The US has offered Ukraine "solid" security guarantees for 15 years with a possibility of an extension, President Volodymyr Zelensky revealed Monday after meeting Donald Trump.

At Mar-a-Lago, Zelensky held talks with Trump, who said a deal to end almost four years of war with Russia was closer than ever.

Though the issues of territory and the future of Ukraine's Moscow-occupied Zaporizhzhia nuclear power plant remain unresolved, Zelensky said he considered the presence of international troops in Ukraine a necessary part of the guarantees – something Russia has rejected in the past.

Still, the Kremlin agreed with Trump's assessment that talks were in their final stages, while repeating its demand for Kyiv to withdraw its forces from eastern Ukraine.

Zelensky said he was hoping for a meeting with European and American officials in Ukraine in the "coming days" to work on documents to end the conflict.

Any deal to end Europe's worst conflict since WWII "must be signed by Ukraine, Russia, the US, and Europe", he said.

Security guarantees are a priority for Kyiv.

"Without security guarantees, this war cannot be considered truly over. We cannot acknowledge that it has ended, because with such a neighbor there remains a risk of renewed aggression," Zelensky said.

He had told Trump the 15-year offer was too short a period for Kyiv.

"I told him that we really want to consider the possibility of 30, 40, 50 years," he revealed. "The president said he would think about it."

Zelensky repeated that Kyiv was ready for "any" format of meetings – including with Vladimir Putin if necessary – but said he still didn't think his Russian counterpart wanted peace.

"On the one hand, he tells the president of the United States that he wants to end the war and that this is his desire," Zelensky said. "And on the other hand...he strikes us with missiles (and) gives instructions to his generals about where to advance."

Putin has for weeks told Russians Moscow was intent on achieving its aims in Ukraine by force if diplomacy fails.

Moscow wants to keep all the territory it occupies in Ukraine as well as be handed lands in eastern Ukraine still controlled by Kyiv.

The Kremlin on Monday again called for Ukraine to withdraw from unoccupied parts of Donbas, warning that "Ukraine is losing territory and will continue to do so."

It said it expected Putin and Trump to speak by phone in the "very near future."

The current 20-point plan, revised after weeks of intense US-Ukrainian negotiations, would stop the war at the current frontlines in the eastern Donbas region and set up a demilitarized area, while Russia has long demanded territorial concessions.