Syria says the US-led war will fail to wrest control of the whole of Iraq and would draw popular resistance across the Arab world.
In an interview with Lebanon's as-Safirnewspaper on Thursday, Syrian President Bashar al-Assad said Washington's attitude towards Syria, which it has long deemed a state sponsor of terrorism, was constantly shifting as its interests changed.
"The United States and Britain will not be able to control all of Iraq. There will be much tougher resistance," Mr Assad said.
"But if the American-British designs succeed - and we hope they do not succeed and we doubt that they will succeed - there will be Arab popular resistance anyway and this has begun".
Syria, a staunch opponent of the week-old war to topple Iraqi President Saddam Hussein, has criticised other Arab leaders for failing to support its efforts to avert what Mr Assad called "outright occupation and flagrant aggression".
Arabs angry over the US-led attack on Iraq have protested almost daily since the war began last Thursday. Several demonstrations have turned on the embassies of some Gulf Arab countries such as Kuwait and Qatar, from which the US-led war has partly been launched and run.
Syria, currently the only Arab member of the UN Security Council, has faced US pressure to back down in its opposition to a war on its neighbour and economic partner.
Syria has said it supports the US "war on terror" launched after the September 11th, 2002, attacks but defends radical Palestinian groups it hosts, and Lebanon's Hizbollah guerrilla group, as legitimate resistance to Israel.