Russia’s president Vladimir Putin is open to peace with Ukraine but his priority remains achieving Moscow’s goals, Kremlin spokesperson Dmitry Peskov said after US president Donald Trump issued his 50-day ultimatum for a ceasefire.

Britain and Germany are set to pledge new air defense systems for Ukraine as the UK government pushes for a “50-day drive” to arm Kyiv and bring Russian President Vladimir Putin to the negotiating table.

Putin’s refusal to compromise on Ukraine, say analysts, is a colossal error costing Russia regional influence, lucrative energy markets and its place in the world.

Peskov also addressed recent comments by US President Donald Trump, noting that the world has grown accustomed to his sometimes “harsh” rhetoric.

A former Russian prime minister has said Vladimir Putin may be forced to agree a peace deal to end the war with Ukraine by the end of the year. Mikhail Kasyanov said Russia’s “contracting” economy meant the country’s president may have no option but to seek a settlement to stop the hostilities.

US President Donald Trump’s 50-day pause ahead of possible secondary sanctions on Russia gifts the Kremlin a window to exploit the incremental gains of recent weeks in Ukraine’s east.

Vladimir Putin’s conduct has prompted Donald Trump’s shift as Russia’s war effort in Ukraine has gotten only more aggressive.

President Donald Trump announced this week that the U.S. will send Patriot air-defense missiles to Ukraine and threatened new tariffs on Russia. Will Vladimir Putin back down? What should Trump's next move be? And what does the future hold for Ukraine? Newsweek contributors Daniel R. DePetris and Dan Perry debate: