"Nobody officially invited the United States to Syria. And if their mission fails, that will be their own fault," Zeman said in an interview with the online edition of the Parlamentni Listy newspaper.
Zeman noted that the Syrian ceasefire deal could be concluded only with the moderate opposition, but not with the Islamist groups. However, unlike the US side, which believes in the existence of the Syrian moderate opposition, Zeman said he believed there were only radical groups in the Arab republic.
He also stressed that the Russian anti-terror campaign in Syria was legitimate, as it was the Syrian government who asked Moscow for assistance.
Syria has been mired in civil war since 2011, with opposition factions and Islamist terrorist groups such as Islamic State and the Nusra Front, now known as Jabhat Fateh al Sham, both outlawed in Russia, fighting the Syrian Army.
A US-led international coalition has been conducting airstrikes against IS in Iraq and Syria since 2014, without seeking approval from the UN Security Council or the Syrian government. Russia has been conducting an aerial campaign against terrorists in Syria since September 30, 2015 at Syrian President Bashar Assad's request.