IT HAS been a month since the White House informed journalists that President Obama had decided to supply Syrian rebels with light arms. Since then, the regime has launched a bloody new offensive in the city of Homs, using heavy artillery and rockets to attack residential areas held by the rebels. Thousands of people have been killed, adding to a death toll approaching 100,000. President Bashar al-Assad has been boasting of his military successes and of the failure of outside powers to bring down his regime. Meanwhile, the United States has failed to deliver any of the promised munitions to beleaguered rebel forces — “not even a single bullet,” one source told The Post’s David Ignatius.

The delay can be attributed in part to congressional resistance: According to reporting by The Post’s Karen DeYoung, the administration’s plan has drawn objections from members of the House and Senate intelligence committees, which are responsible for reviewing covert operations. But the larger problem is an extraordinary failure of leadership by Mr. Obama. While deciding on intervention in a fateful Middle East war, the president has chosen a minimalist option likely to fail while declining to publicly explain or justify his actions.

A decision to intervene in a foreign war, even in a small way, ought to be the subject of a direct presidential address to the country and an open debate in Congress. Yet the news that the United States would, after more than two years of dithering, finally provide direct military aid to rebels came in a conference call with reporters by White House aide Ben Rhodes on June 13. While letting the world know about it, Mr. Obama chose to designate his action as covert, stifling public discussion and restricting details on the arms supplies to members of the congressional intelligence committees. In some of his most extensive public comments on Syria since then, in an interview with PBS’s Charlie Rose on June 17, Mr. Obama spent much of his time arguing the case against intervention, insisting that “we have to not rush into one more war in the Middle East.”

Little wonder that congressmen on both sides of the intervention issue are pushing back. Some worry that Mr. Obama is placing the United States on a slippery slope. Others, such as Senate Armed Services Committee Chairman Carl Levin (D-Mich.), argue that the administration should be working with allies to take much stronger measures, including striking at Syrian planes and artillery. Both sides are probably right. The strategy of arming the rebels that Mr. Obama has embraced — but not implemented — is not enough to achieve his goal of forcing the Syrian regime to accept a negotiated political transition that would exclude Mr. Assad.

Mr. Obama’s fecklessness on Syria has baffled and alarmed important U.S. allies, including Turkey and Israel, which wonder if the United States can still be counted on as a force in the region. It has emboldened not just Mr. Assad but also Iran, which has been stepping up its own intervention in Syria in the belief that it will not be countered. Now the president is failing to deliver even on the modest action he decided on. It’s a spectacle that can only harm U.S. standing in the Middle East — and prolong Syria’s bloodshed.