President Barack Obama said the United States "underestimated" the rise of Islamic State and other Syrian-based militants, and "overestimated" Iraq's ability to fight them.
Obama told CBS television's Sunday it is a myth that if the United States had armed the moderate Syrian rebels two years ago, as some in Washington urged, Syria would be fine today.
The president blamed the situation in Iraq, in part, on former prime minister Nouri al-Maliki. He said the prime minister squandered an opportunity to unify the country.
Obama said Maliki was suspicious of Sunnis and Kurds and more interested in consolidating his Shi'ite support than putting together a unity government.
The U.S. leader said Syrians, Iraqis and others in the region must think about what political accommodation means. He said young men who only think about whether they are Sunnis or Shi'ites should instead be concerned about getting an education and a good job.
Earlier Sunday, U.S.-led airstrikes hit three oil refineries near Syria's border with Turkey early Sunday in the ongoing offensive against Islamic State militants.
The Britain-based Syrian Observatory for Human Rights said the attacks occurred shortly after midnight, adding that they also hit a plastics factory.
Also on Sunday, U.S. lawmakers stepped up calls for congressional authorization of Obama's war against Islamic State militants in Iraq and Syria, amid signs the United States and its allies face a long and difficult fight.
U.S. House Speaker John Boehner of Ohio told ABC's that he believed Obama had the legal authority for strikes against Islamic State militants, but would call lawmakers back from their districts if Obama sought a resolution backing the action.
“I think he does have the authority to do it. But ... this is a proposal the Congress ought to consider,” Boehner said, warning that the United States could eventually be dragged into another ground war in the region.
Obama and other U.S. officials have said they believe no further vote to authorize force is needed, but political analysts warn that the war could dampen participation by anti-war Democrats in the November elections.
Senator Chris Murphy, a Connecticut Democrat and member of the Senate Foreign Relations Committee, told CNN that Congress should debate the issue because of uncertainty about how long the U.S. military would remain engaged in Syria.
“There are some serious questions that we have to ask,” Murphy said. “You need a realistic political strategy. And I just don't think we have that today in Syria.”
Senator John Barrasso, a Wyoming Republican and member of the Foreign Relations Committee, urged Obama to follow the lead of British Prime Minister David Cameron in recalling the British parliament.
“I think the president has an obligation to call us back tomorrow to start this debate,” Barrasso said.