US President Donald Trump has touted his meeting with Ukrainian and European leaders on Monday at the White House as "a very good, early step." He is trying to organize a bilateral summit between Russia and Ukraine, but he says a ceasefire is not necessary for that to happen.

Trump interrupted his talks with the leaders to call Russian President Vladimir Putin. Russia's state-run TASS news agency quotes presidential aide Yury Ushakov as saying the 40-minute talk was "frank and very constructive. "

The office of Ukrainian President Volodymyr Zelenskyy posted online that the Kremlin has proposed holding a trilateral summit. Zelenskyy says he is ready for talks in any format, and he stressed that territorial issues will be worked out between the two sides.

White House Press Secretary Karoline Leavitt said at a news conference on Tuesday, "The president has definitively stated US boots will not be on the ground in Ukraine, but we can certainly help in the coordination and perhaps provide other means of security guarantees to our European allies."

Trump has not mentioned the details of those guarantees, but Zelenskyy has hinted at a "package of weapons." He expects the details to be worked out "within the next week to 10 days."

Russian Foreign Minister Sergey Lavrov told state-run television that it is necessary to make utmost preparations for the summit.

An expert in politics believes that the process will move forward at Putin's pace. Keio University Professor Tsuruoka Michito, an expert in international security and contemporary European politics, said: "I think it's not so easy for Putin to make a decision to meet Zelenskyy. How much time will Russia be able to delay in a way that doesn't make President Trump angry? I think that is their idea."

German Chancellor Friedrich Merz said the summit will take place in the next two weeks. It would be the first meeting between Putin and Zelenskyy since the invasion began. However, it remains unclear whether the summit will be realized.