Ukrainian President Volodymyr Zelenskyy concluded his talks with US President Donald Trump without a peace deal, but he said US and Ukrainian teams will meet again soon and that a gathering of leaders -- including those from Europe -- will be held in Washington next month. Zelenskyy, on December 28, posted on social media that "we had a substantive discussion on all issues," including matters concerning all-important security guarantees, at Trump's Mar-a-Lago resort in Palm Beach, Florida. "We discussed all the aspects of the peace framework and…