U.S. and European military planners have begun exploring post-conflict security guarantees for Ukraine, U.S. officials and sources said on Tuesday, following President Donald Trump's pledge to help protect the country under any deal to end Russia's war. 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 said the Pentagon is carrying out planning exercises on the support Washington could offer beyond providing weapons. But they cautioned that it would take time for U.S. and European planners to determine what would be both militarily feasible and acceptable to the Kremlin. One option was sending European forces to Ukraine but putting the U.S. in charge of their command and control, two sources familiar with the matter said. The sources added that the troops would not be under a NATO banner but operate under their own nations' flags. The Pentagon and NATO did not immediately respond to a request for comment on the idea.

In a press briefing, the White House said that the United States could help coordinate a security guarantee for Ukraine. Russia's Foreign Ministry has ruled out the deployment of troops from NATO countries to help secure a peace deal.