US and European officials will immediately work on providing Ukraine with robust security guarantees to open a path for a landmark meeting between presidents Vladimir Putin and Volodymyr Zelenskiy, according to people familiar with the matter.

Plans for security guarantees for Ukraine appear to be triggering unease in Moscow, which repeated objections to any role for forces from NATO countries.

Ukraine and its European allies have been buoyed by Trump's promise during a summit on Monday of security guarantees for Kyiv, but many questions remain unanswered. Officials told Reuters that the Pentagon is carrying out planning exercises on the support Washington could offer beyond providing weapons.