Syria will resist any ground incursion into its territory and send the aggressors home “in coffins,” its foreign minister said Saturday in comments clearly aimed at Sunni Arab countries that have said they were ready to join such an operation.

Foreign Minister Walid al-Moualem also told a news conference a cease-fire in the Syria conflict would be virtually impossible while rebels opposed to President Bashar Assad’s government were able to pass freely across the borders with Turkey and Jordan.

“Any ground intervention onto Syrian land without the agreement of the Syrian government is an act of aggression ... and we regret that those [who do so] will return to their countries in coffins,” he said.

Saudi Arabia and Bahrain, both ruled by Sunni Muslim monarchies, said this week they were ready to participate in any ground operations in Syria if the U.S.-led coalition fighting Islamic State group militants in Syria and Iraq decides to start such operations.

“I don't think they will do what they say about using ground forces, but at the same time, when I look at their crazy decisions made not just in Yemen but in other areas nothing can be ruled out,” Moualem said, alluding to a Saudi-led military campaign against Iran-allied Houthi rebels in Yemen.

Moualem also cited Russian Foreign Minister Sergei Lavrov who recently said a cease-fire in Syria was very unlikely until the borders with Turkey and Jordan have been sealed.

Rebel groups fighting Assad have received supplies via both Turkey and Jordan. Russia's military intervention in the Syrian conflict in support of Assad has helped Damascus to reclaim territory previously lost to rebels.