Chinese philosopher Sun Tzu famously advised that during times of conflict, “build your opponent a golden bridge to retreat across."

As America contemplates military force against the Assad regime in Syria, is there a potential golden bridge or dignified accommodation to offer Iran, Bashar al-Assad’s indispensable supporter?

Iran considers Syria its key geopolitical ally — a partner in an “Axis of Resistance” — and its critical geographic link to the Lebanese Shiite militia Hezbollah, Tehran’s prized regional asset.

While the arrival of more pragmatic Iranian politicians — namely President Hassan Rouhani and U.S.-educated foreign minister Javad Zarif — has understandably renewed hopes for diplomacy with Tehran, Iran’s alliance with Syria has long been maintained by the country’s Revolutionary Guards, not its diplomats.

Qassim Suleimani, the commander believed to manage Iranian operations in Syria, just yesterday declared that Tehran “will support Syria to the end.” Even more moderate figures, like former president, Ali Akbar Hashemi Rafsanjani, have implored continued support for Syria as a bulwark against Israel.

In this context, successful diplomatic engagement with Iran is hampered by the fact that outside powers — be it the U.S., Russia, or the Arab world — cannot offer Tehran assurances that a post-Assad government in Syria will remain friendly to Iranian interests.

Tehran's complicity in helping Assad kill tens of thousands of rebels has significantly diminished this prospect.

Ironically, the collapse of the Assad regime would produce a common interest for Washington and Tehran in making sure that radical Sunni Islamists, who hate Shiite Iran even more than America, do not rule Damascus.

Until then, as long as Iran sees itself embroiled in a zero-sum game in Syria, a half-way meeting point, however desirable, will likely remain elusive.

This article was originally published in the New York Times.