Military chiefs from the United States and a number of European countries have developed military options on Ukraine and will be presenting them to their respective national security advisers, a U.S. official told Reuters on Thursday.

Reuters has previously reported U.S. and European military planners have begun exploring post-conflict security guarantees for Ukraine, following President Donald Trump's pledge to help protect the country under any deal to end Russia's war in Ukraine.

"These options will be presented to each nation's respective national security advisers for appropriate consideration in ongoing diplomatic efforts," the official said.

The official said meetings between the chiefs of defense for the United States, Finland, France, Germany, Italy, United Kingdom, and Ukraine took place in Washington, D.C., between Tuesday and Thursday. Ukraine and its European allies have been buoyed by Trump's promise during a summit Monday of security guarantees for Kyiv, but many questions remain unanswered.

Officials have cautioned 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, sources have told Reuters. Russia's Foreign Ministry has ruled out the deployment of troops from NATO countries to help secure a peace deal.