US President Donald Trump had vowed to bring a swift end to Russia’s more than three-year-long war against Ukraine, but has failed to force a peace agreement during his first 100 days in office as Moscow and Kyiv both reject elements of his administration’s proposals.

If Trump walks away, or if Kyiv rejects a deal and keeps fighting with European support, it won’t necessarily mean “the collapse of Ukraine” although more people will almost certainly die if the U.S. pulls its air defenses and intelligence-sharing capabilities, Heisbourg said.