The Iran-backed Houthis’ swift advance in Yemen and attacks on Saudi Arabia have left the Gulf Arab kingdom with few options to respond, all of which carry heavy costs.

The key message emanating from the kingdom is that Riyadh does not want an all-out war, experts say, but the Houthis’ emboldened behavior may nonetheless drag the Gulf state into a wider conflict.

All signs now “point to a large-scale Saudi retaliation, and that likelihood is increasing by the day,” Mohammed Al-Basha, an expert on Yemen and Washington, DC-based risk adviser, told CNN.

“At this point they don’t have an option,” he said.

This week, the Yemeni rebel group captured the strategic Perim Island, at the mouth of the Red Sea, along with the port town of Mocha as it sought to take control of the Bab al-Mandeb strait, a key energy route.