"You can say Trump and his friend Putin are the founder of ISIS, which would probably be more accurate than calling out the commander-in-chief in that way", she concluded. "He was the most valuable player", Trump said, using an acronym for the militant Islamist group, adding Clinton also deserved the award.
Trump said in that instance as well that he was being sarcastic.
He further said only Mr. Trump could give an answer to it, and he will give it to tweet and statement.
Republican U.S. presidential nominee Donald Trump speaks at an American Renewal Project event at the Orlando Convention Center in Orlando, Florida August 11, 2016.
Yet on Thursday, he was reduced to citing a poll that showed him a few points behind Ms Clinton and arguing that the race was close.
Clinton is looking to take advantage by expanding into traditionally Republican states, seeking a sweeping victory in November.
Trump: "I don't care".
McCaskill immediately explained why Clinton and Obama pulled the troops out of Iraq - which Trump believes led to the rise of ISIS - while getting in a snarky dig at the GOP nominee. In an interview with radio host Hugh Hewitt, the real estate mogul was asked about his comments and whether he actually meant that Obama "created the vacuum, he lost the peace", which created the conditions in which the Islamic State could emerge.
Trump has previously backtracked on controversial comments by implying he was only joking.
On Monday 50 prominent Republican national security officials, including a former Central Intelligence Agency director, called Trump unqualified to lead the country and said he would be "the most reckless president in American history".
Trump is on the trail Friday in Pennsylvania - a must win state. The officials weren't authorized to comment publicly and requested anonymity.