WASHINGTON—White House concerns that Iran's hand is being strengthened by recent events in the Middle East is central to its response to the turmoil, say U.S., European, and Arab officials.

President Barack Obama's decision last week to use military force against Libyan leader Moammar Gadhafi's forces was made in part by his administration's fear that Western inaction could further embolden Tehran, these officials say.

Sunni-majority...