NEW YORK—JPMorgan could lose about $1 billion on its Russia exposure, Chief Executive Jamie Dimon said on Monday, detailing the extent of the bank’s potential losses from the conflict in Ukraine for the first time. In his keenly watched annual letter to shareholders, the chairman and chief executive of the biggest U.S. bank by assets also urged the United States to increase its military presence in Europe and reiterated a call for it to develop a plan to ensure energy security for itself and its allies. Dimon did not provide a time frame for JPMorgan’s potential Russia losses but said the bank was concerned about the secondary impact of Russia’s invasion of Ukraine on companies and countries. Russia calls its actions a “special operation.” Global banks have detailed their exposure to Russia in recent weeks but Dimon is the most high-profile world business leader yet to comment on the broader …