Russian President Vladimir Putin has praised US President Donald Trump's efforts to end the war in Ukraine, more than three years after Moscow launched its invasion, as the two leaders prepared for a pivotal US-Russia summit on Friday in Alaska.

Following a meeting on Thursday with top government officials on the summit, Putin said in a short video released by the Kremlin that the Trump administration was making 'quite energetic and sincere efforts to stop the hostilities' and to 'reach agreements that are of interest to all parties involved.' Putin also suggested that 'long-term conditions of peace between our countries, and in Europe, and in the world as a whole,' could be reached under an agreement with the US on nuclear arms control.

In Washington, Trump said there was a 25 per cent chance that the summit would fail, but he also floated the idea that, if the meeting succeeds, he could bring Ukrainian President Volodymyr Zelenskyy to Alaska for a subsequent, three-way meeting. In a radio interview with Fox News, Trump also said he might be willing to stay in Alaska longer, depending on what happens with Putin. Meanwhile, Zelenskyy and other European leaders worked to ensure their interests are taken into account when Trump and Putin meet in Anchorage.