By Doina Chiacu

WASHINGTON (Reuters) – Republican presidential candidate Donald Trump called President Barack Obama and Democratic candidate Hillary Clinton “co-founders” of Islamic State on Thursday, in remarks certain to ignite fresh criticism of his campaign style.

The New York real estate developer has previously criticized Obama and Clinton, secretary of state from 2009-13, for how the United States pulled out of Iraq after the war, saying it helped create the militant Islamist group that has seized swaths of Iraq and Syria.

The idea that a sitting U.S. president created a militant group determined to kill Americans and other Westerners took that criticism to a new level. Trump first made the assertion in a speech Wednesday night in Florida. He repeated it in an interview Thursday morning with CNBC.

His remarks followed a troubled week for the Republican candidate. Party leaders urged Trump to focus on the campaign to beat Clinton after he drew strong criticism for a persistent confrontation with the family of Muslim American soldier who died in Iraq and for his initial refusal to support prominent Republican candidates in their primary races.

Recent opinion polls have shown Trump losing ground to Clinton, a former U.S. senator and first lady, in the race for the Nov. 8 election. An average of polls by RealClearPolitics has Clinton 7.7 percentage points ahead, at 48 percent to his 40.3 percent.

“He (Obama) was the founder of ISIS. And so was she. I mean I call them co-founders,” said Trump, who says he opposed the Iraq war. “He shouldn’t have gotten out way he got out. It was a disaster, what he did,” he told CNBC.

Obama had opposed the Iraq war and campaigned for the White House in 2008 on a promise to end it. The United States pulled out combat troops in 2011.

Islamic State in Iraq and Syria, also known as ISIS or ISIL, had its roots in the al Qaeda insurgency that arose after the United States led an invasion of Iraq in 2003. Known for its brutality, the group in 2014 declared an Islamic caliphate in Syria and Iraq, where fighting continues to rage.

Clinton spokesman Jesse Lehrich, in response to Trump’s comments, pointed to U.S. advances against the militant group in Libya this week. “FYI – U.S.-backed militias retook ISIS’s stronghold in Libya today thanks to Obama-authorized air strikes,” he said in a tweet late on Wednesday.

Trump did not back down, asking on CNBC: “Is there something wrong with saying that? Why – are people complaining that I said he was the founder of ISIS? All I do is tell the truth, I’m a truth teller.”

Supporters of Trump, who has never held elected office, like the combative and often insulting style that has drawn him wide criticism, including from some in his party. He said that if that style costs him the election in 90 days, he goes back to a good life.

“It’s not what I’m looking to do – I think we’re going to have a victory but we’ll see,” he said.

In a wide-ranging interview, Trump also said the United States will continue engaging in free trade if he is elected.

“We are absolutely going to keep trading. I am not an isolationist … I’m a fair trader,” Trump said.

(Reporting by Doina Chiacu and Susan Heavey; Editing by Chizu Nomiyama and Frances Kerry)

Photo: Republican U.S. presidential candidate Donald Trump speaks at a campaign rally in Raleigh, North Carolina, U.S., July 5, 2016. REUTERS/Joshua Roberts