WASHINGTON — Frustrated by a diplomatic logjam and a bloody Syrian offensive, Republican Sen. John McCain on Monday urged the United States to launch airstrikes against President Bashar Assad’s regime to force him out of power — a call for dramatic military intervention that wasn’t supported by the Obama administration or its European or Arab partners.

McCain’s statement on the Senate floor came as the U.S. and European governments pleaded for Russia’s Vladimir Putin to rethink his anti-interventionist stance on Syria, in what appeared to be an increasingly desperate effort for consensus among world powers to stop a crackdown that has killed more than 7,500 people. Hundreds fled to neighboring Lebanon on Monday fearing they’d be massacred in their homes.

But the trans-Atlantic calls for Russia to abandon its opposition to strong U.N. action were delivered at a curious time: a day after Putin showed his strength by resoundingly winning re-election as president, a position he held from 2000 to 2008. Even the modest aim of gaining Russian support for a humanitarian strategy in Syria faced renewed resistance Monday — showing just how limited the diplomatic options were despite the ongoing violence.

McCain’s strategy would be far more direct, though it’s unclear how popular it would be. His statement was as much a critique of President Barack Obama as a rallying call for an international military campaign, accusing the president of being too soft on Assad.

McCain, the GOP’s presidential nominee in 2008 and his party’s senior member on the Senate Armed Services Committee, said the U.S. should change policy by arming Syria’s rebels and spearheading a military effort to support them.

“The only realistic way to do so is with foreign airpower,” McCain concluded. “The United States should lead an international effort to protect key population centers in Syria, especially in the north, through airstrikes on Assad’s forces.”

McCain’s proposal will likely divide American lawmakers, many of whom opposed a similar operation in Libya last year. Even if it were championed by the Obama administration and its NATO allies, the plan would divide other countries hostile to the Assad regime but unwilling to support another Western military intervention in the Muslim world. And it would be anathema to Russia, which sees Syria as its primary ally in the Middle East.