The Obama administration’s policy on Syria is a strategic disaster that undercuts its entire foreign policy from the Middle East to Asia. If you think I’m exaggerating, read on.

Bashar al-Assad — whose exit President Obama has demanded for more than a year — is poised to crush the Syrian rebellion, using money, weapons and manpower provided by Russia, Iran and the Lebanese terrorist group Hezbollah. Washington claims to support moderate rebel fighters, but so far it has delivered only food rations and medical kits — no help against Assad’s missiles and bombs.

After months of debate, White House officials finally announced last week they will send military aid to the rebels (supposedly because Assad used chemical weapons). But the announcement made the administration only look feckless: The aid will include small arms and ammo, but not the heavy weapons required to stall Assad.

Antiaircraft weapons, crucial for holding off Assad’s air assaults, aren’t even being considered. This plan is too little, too late.

Meanwhile, the White House “strategy” for Syria — based on the hope that Moscow would push Assad to relinquish power at peace talks in Geneva — has collapsed. Why would Assad (or Russian leader Vladimir Putin) bend when victory is in sight?

Obama doesn’t seem to grasp Syria has become a strategic contest the whole world is watching — one that involves core U.S. security interests. The president’s indecision on Syria has signaled to Russia, Iran and Hezbollah (not to mention China and the Taliban) they can ignore Obama’s tough talk. It has also strained relations with Arab allies who fear Iran and want to see its hold on Syria broken.

Sen. Bob Casey, D-Pa., who has long been out front on Syria, spoke last week with Gen. Salim Idris, the military leader of the Syrian opposition, who urged America to send antitank and antiaircraft weapons to prevent rebel strongholds from falling.

“If the U.S. is not prepared to provide more robust assistance,” Casey said, “I fear that the moderate opposition forces will be defeated.” That would embolden Iran and Hezbollah to act more aggressively throughout the region, undercutting core U.S. security interests and threatening Israel. “The time for U.S. action is overdue,” Casey insisted, rightly. “Assad must go, but this will not happen without decisive leadership from the United States.”

Yet, two years and 93,000 Syrian deaths later, Obama’s advisers still dither, treating the conflict as a local matter, not a wider strategic threat. No doubt the options are daunting, and, at this late date, the chances slimmer than ever for a stable Syria. But the administration’s reluctance is based on refutable myths.

Myth One: The lesson of Iraq is that we shouldn’t get involved in another Mideast conflict.

Reality: The cases are critically different. We invaded and occupied Iraq. In Syria, no one is calling for boots on the ground. The opposition is fractured, but includes militias headed by former army officers or moderate Muslim civilians. The CIA spent a year vetting rebel commanders and had identified several responsible ones by last fall. But Obama rejected proposals from David Petraeus and Hillary Clinton to arm them.

Myth Two: Arming rebels would undercut peace prospects.

Reality: The only hope for serious peace talks lies in convincing Assad and his backers in Moscow that he might lose.

Myth Three: If we send arms to the rebels, they may fall into al-Qaida’s hands.

Reality: Jihadi groups linked to al-Qaeda already have plenty of weapons, provided by wealthy Gulf Arabs. It’s the more moderate commanders who are short of weapons. Indeed, U.S. policy has undercut the moderates and enabled jihadis to become the most prominent rebels, even though their numbers are relatively small.

Myth Four: It’s time to let someone else do it.

Reality: Outsourcing the arming of rebels to Qatar and Saudi Arabia led to the results we most feared. Lacking strong U.S. oversight, the Gulf states armed their favorite militias, often hard-line Islamists. They also ignored U.S. pleas to unify the militias into a coherent force. Meanwhile, the Europeans and Turks remain reluctant to help unless Obama takes the lead.

Myth Five: Arming the rebels will fuel a sectarian war between Shiites and Sunnis.

Reality: Helped by Iran and Hezbollah, Assad is provoking sectarian slaughter to convince Syrians that they need a dictator. The longer this war goes on, the greater the bloodshed. It has already spread beyond Syria’s borders, with dangerous implications for the entire Middle East.

Myth Six: We can afford to stay uninvolved and let the Syrians sort it out themselves.

Reality: Syria has already become a proxy war, with Iran and Moscow testing Obama’s willingness to defend U.S. interests. A swift delivery of antiaircraft and antitank weapons to vetted rebel commanders would make Assad’s allies think twice about the dangerous game they are playing. And it would counter the growing global perception that Obama has abandoned America’s historic leadership role.

Trudy Rubin is a columnist and editorial-board member for the Philadelphia Inquirer.